From d4d355ca2d69057423ac652e9873839886000c30 Mon Sep 17 00:00:00 2001
From: Manuel Kaufmann <humitos@gmail.com>
Date: Thu, 21 Dec 2017 13:50:53 -0500
Subject: [PATCH 01/12] Check versions used to create the venv and auto-wipe

---
 .../doc_builder/python_environments.py        | 61 ++++++++++++++++++-
 readthedocs/projects/tasks.py                 |  9 ++-
 2 files changed, 66 insertions(+), 4 deletions(-)

diff --git a/readthedocs/doc_builder/python_environments.py b/readthedocs/doc_builder/python_environments.py
index 74879ac4ce7..94959b8b6c6 100644
--- a/readthedocs/doc_builder/python_environments.py
+++ b/readthedocs/doc_builder/python_environments.py
@@ -1,12 +1,17 @@
+# -*- coding: utf-8 -*-
 """An abstraction over virtualenv and Conda environments."""
 
-from __future__ import absolute_import
-from builtins import object
+from __future__ import (
+    absolute_import, division, print_function, unicode_literals)
+
+import json
 import logging
 import os
 import shutil
+from builtins import object
 
 from django.conf import settings
+from packaging.version import Version
 
 from readthedocs.doc_builder.config import ConfigWrapper
 from readthedocs.doc_builder.loader import get_builder_class
@@ -38,7 +43,6 @@ def _log(self, msg):
                          msg=msg))
 
     def delete_existing_build_dir(self):
-
         # Handle deleting old build dir
         build_dir = os.path.join(
             self.venv_path(),
@@ -47,6 +51,13 @@ def delete_existing_build_dir(self):
             self._log('Removing existing build directory')
             shutil.rmtree(build_dir)
 
+    def delete_existing_env_dir(self):
+        venv_dir = self.venv_path()
+        # Handle deleting old venv dir
+        if os.path.exists(venv_dir):
+            self._log('Removing existing venv directory')
+            shutil.rmtree(venv_dir)
+
     def install_package(self):
         if self.config.install_project:
             if self.config.pip_install or getattr(settings, 'USE_PIP_INSTALL', False):
@@ -96,6 +107,50 @@ class Virtualenv(PythonEnvironment):
     .. _virtualenv: https://virtualenv.pypa.io/
     """
 
+    @property
+    def is_obsolete(self):
+        """
+        Determine if the Python version of the venv obsolete.
+
+        It checks the the data stored at ``environment.json`` and compares it
+        against the Python version in the project version to be built and the
+        Docker image used to create the venv against the one in the project
+        version config.
+
+        :returns: ``True`` when it's obsolete and ``False`` otherwise
+
+        :rtype: bool
+        """
+        # Always return True if we don't have information about what Python
+        # version/Docker image was used to create the venv as backward
+        # compatibility.
+        if not os.path.exists(self.environment_json_path()):
+            return False
+
+        try:
+            environment_conf = json.load(self.environment_json_path())
+            env_python_version = Version(environment_conf['python']['version'])
+            env_build_image = Version(environment_conf['build']['image'])
+        except (TypeError, KeyError, json.decoder.JSONDecodeError):
+            return False
+
+        # If the user define the Python version just as a major version
+        # (e.g. ``2`` or ``3``) we won't know exactly which exact version was
+        # used to create the venv but we can still compare it against the new
+        # one coming from the project version config.
+        return any([
+            env_python_version != Version(self.config.python_version),
+            env_build_image != self.config.build_image,
+        ])
+
+    def environment_json_path(self):
+        return os.path.join(
+            self.project.doc_path,
+            'envs',
+            self.version.slug,
+            'environment.json',
+        )
+
     def venv_path(self):
         return os.path.join(self.project.doc_path, 'envs', self.version.slug)
 
diff --git a/readthedocs/projects/tasks.py b/readthedocs/projects/tasks.py
index 0bf82c85500..5f077f25a28 100644
--- a/readthedocs/projects/tasks.py
+++ b/readthedocs/projects/tasks.py
@@ -435,7 +435,14 @@ def setup_environment(self):
                 version=self.version,
                 max_lock_age=getattr(settings, 'REPO_LOCK_SECONDS', 30)):
 
-            self.python_env.delete_existing_build_dir()
+            # Check if the python version/build image in the current venv is the
+            # same to be used in this build and if it differs, wipe the venv to
+            # avoid conflicts.
+            if self.python_env.is_obsolete:
+                self.python_env.delete_existing_venv_dir()
+            else:
+                self.python_env.delete_existing_build_dir()
+
             self.python_env.setup_base()
             self.python_env.install_core_requirements()
             self.python_env.install_user_requirements()

From 1541bf0683c8dfdea050e36b1808095462818948 Mon Sep 17 00:00:00 2001
From: Manuel Kaufmann <humitos@gmail.com>
Date: Thu, 21 Dec 2017 15:20:18 -0500
Subject: [PATCH 02/12] Save environment.json file

---
 .../doc_builder/python_environments.py        | 47 +++++++++++++------
 readthedocs/projects/tasks.py                 |  1 +
 2 files changed, 33 insertions(+), 15 deletions(-)

diff --git a/readthedocs/doc_builder/python_environments.py b/readthedocs/doc_builder/python_environments.py
index 94959b8b6c6..03a11df88fb 100644
--- a/readthedocs/doc_builder/python_environments.py
+++ b/readthedocs/doc_builder/python_environments.py
@@ -98,14 +98,14 @@ def venv_bin(self, filename=None):
             parts.append(filename)
         return os.path.join(*parts)
 
-
-class Virtualenv(PythonEnvironment):
-
-    """
-    A virtualenv_ environment.
-
-    .. _virtualenv: https://virtualenv.pypa.io/
-    """
+    def environment_json_path(self):
+        """
+        Return the path to the ``environment.json`` file for this venv.
+        """
+        return os.path.join(
+            self.venv_path(),
+            'environment.json',
+        )
 
     @property
     def is_obsolete(self):
@@ -143,13 +143,30 @@ def is_obsolete(self):
             env_build_image != self.config.build_image,
         ])
 
-    def environment_json_path(self):
-        return os.path.join(
-            self.project.doc_path,
-            'envs',
-            self.version.slug,
-            'environment.json',
-        )
+    def save_environment_json(self):
+        """
+        Save on disk Python and build image versions used to create the venv.
+        """
+        data = {
+            'python': {
+                'version': self.config.python_version,
+            },
+            'build': {
+                'image': self.config.build_image,
+            },
+        }
+        with open(self.environment_json_path(), 'w') as fpath:
+            json.dump(data, fpath)
+
+
+
+class Virtualenv(PythonEnvironment):
+
+    """
+    A virtualenv_ environment.
+
+    .. _virtualenv: https://virtualenv.pypa.io/
+    """
 
     def venv_path(self):
         return os.path.join(self.project.doc_path, 'envs', self.version.slug)
diff --git a/readthedocs/projects/tasks.py b/readthedocs/projects/tasks.py
index 5f077f25a28..a376e30ff38 100644
--- a/readthedocs/projects/tasks.py
+++ b/readthedocs/projects/tasks.py
@@ -444,6 +444,7 @@ def setup_environment(self):
                 self.python_env.delete_existing_build_dir()
 
             self.python_env.setup_base()
+            self.python_env.save_environment_json()
             self.python_env.install_core_requirements()
             self.python_env.install_user_requirements()
             self.python_env.install_package()

From 85d76034ba5d5190ed308c3b9217bb8c39efd50c Mon Sep 17 00:00:00 2001
From: Manuel Kaufmann <humitos@gmail.com>
Date: Thu, 21 Dec 2017 17:07:06 -0500
Subject: [PATCH 03/12] Open file properly

---
 readthedocs/doc_builder/python_environments.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/readthedocs/doc_builder/python_environments.py b/readthedocs/doc_builder/python_environments.py
index 03a11df88fb..45ef8f85b82 100644
--- a/readthedocs/doc_builder/python_environments.py
+++ b/readthedocs/doc_builder/python_environments.py
@@ -128,10 +128,11 @@ def is_obsolete(self):
             return False
 
         try:
-            environment_conf = json.load(self.environment_json_path())
+            with open(self.environment_json_path(), 'r') as fpath:
+                environment_conf = json.load(fpath)
             env_python_version = Version(environment_conf['python']['version'])
             env_build_image = Version(environment_conf['build']['image'])
-        except (TypeError, KeyError, json.decoder.JSONDecodeError):
+        except (TypeError, KeyError, ValueError):
             return False
 
         # If the user define the Python version just as a major version

From 05c2aed300cdae0578c34e2cfc67a784e898ca7e Mon Sep 17 00:00:00 2001
From: Manuel Kaufmann <humitos@gmail.com>
Date: Thu, 21 Dec 2017 17:07:26 -0500
Subject: [PATCH 04/12] Make it compatible with current master

---
 readthedocs/doc_builder/python_environments.py | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/readthedocs/doc_builder/python_environments.py b/readthedocs/doc_builder/python_environments.py
index 45ef8f85b82..6fc5ce1101e 100644
--- a/readthedocs/doc_builder/python_environments.py
+++ b/readthedocs/doc_builder/python_environments.py
@@ -141,7 +141,8 @@ def is_obsolete(self):
         # one coming from the project version config.
         return any([
             env_python_version != Version(self.config.python_version),
-            env_build_image != self.config.build_image,
+            # TODO: remove getattr when https://github.com/rtfd/readthedocs.org/pull/3339 got merged
+            env_build_image != getattr(self.config, 'build_image', self.version.project.container_image),
         ])
 
     def save_environment_json(self):
@@ -153,7 +154,8 @@ def save_environment_json(self):
                 'version': self.config.python_version,
             },
             'build': {
-                'image': self.config.build_image,
+                # TODO: remove getattr when https://github.com/rtfd/readthedocs.org/pull/3339 got merged
+                'image': getattr(self.config, 'build_image', self.version.project.container_image),
             },
         }
         with open(self.environment_json_path(), 'w') as fpath:

From e99673a4932d7fc2d3f8c4689bd2c43cdcf8bbec Mon Sep 17 00:00:00 2001
From: Manuel Kaufmann <humitos@gmail.com>
Date: Thu, 21 Dec 2017 17:29:45 -0500
Subject: [PATCH 05/12] Minor refactor

---
 .../doc_builder/python_environments.py        | 23 +++++++++++--------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/readthedocs/doc_builder/python_environments.py b/readthedocs/doc_builder/python_environments.py
index 6fc5ce1101e..adb5ee44eae 100644
--- a/readthedocs/doc_builder/python_environments.py
+++ b/readthedocs/doc_builder/python_environments.py
@@ -11,9 +11,9 @@
 from builtins import object
 
 from django.conf import settings
-from packaging.version import Version
 
 from readthedocs.doc_builder.config import ConfigWrapper
+from readthedocs.doc_builder.constants import DOCKER_IMAGE
 from readthedocs.doc_builder.loader import get_builder_class
 from readthedocs.projects.constants import LOG_TEMPLATE
 from readthedocs.projects.models import Feature
@@ -51,7 +51,7 @@ def delete_existing_build_dir(self):
             self._log('Removing existing build directory')
             shutil.rmtree(build_dir)
 
-    def delete_existing_env_dir(self):
+    def delete_existing_venv_dir(self):
         venv_dir = self.venv_path()
         # Handle deleting old venv dir
         if os.path.exists(venv_dir):
@@ -130,32 +130,37 @@ def is_obsolete(self):
         try:
             with open(self.environment_json_path(), 'r') as fpath:
                 environment_conf = json.load(fpath)
-            env_python_version = Version(environment_conf['python']['version'])
-            env_build_image = Version(environment_conf['build']['image'])
+            env_python_version = environment_conf['python']['version']
+            env_build_image = environment_conf['build']['image']
         except (TypeError, KeyError, ValueError):
+            log.error('Unable to read/parse environment.json file')
             return False
 
+        # TODO: remove getattr when https://github.com/rtfd/readthedocs.org/pull/3339 got merged
+        build_image = getattr(self.config, 'build_image', self.version.project.container_image) or DOCKER_IMAGE
+
         # If the user define the Python version just as a major version
         # (e.g. ``2`` or ``3``) we won't know exactly which exact version was
         # used to create the venv but we can still compare it against the new
         # one coming from the project version config.
         return any([
-            env_python_version != Version(self.config.python_version),
-            # TODO: remove getattr when https://github.com/rtfd/readthedocs.org/pull/3339 got merged
-            env_build_image != getattr(self.config, 'build_image', self.version.project.container_image),
+            env_python_version != self.config.python_version,
+            env_build_image != build_image,
         ])
 
     def save_environment_json(self):
         """
         Save on disk Python and build image versions used to create the venv.
         """
+        # TODO: remove getattr when https://github.com/rtfd/readthedocs.org/pull/3339 got merged
+        build_image = getattr(self.config, 'build_image', self.version.project.container_image) or DOCKER_IMAGE
+
         data = {
             'python': {
                 'version': self.config.python_version,
             },
             'build': {
-                # TODO: remove getattr when https://github.com/rtfd/readthedocs.org/pull/3339 got merged
-                'image': getattr(self.config, 'build_image', self.version.project.container_image),
+                'image': build_image,
             },
         }
         with open(self.environment_json_path(), 'w') as fpath:

From d38b5c340aba627ec577f970178679d1c40922f6 Mon Sep 17 00:00:00 2001
From: Manuel Kaufmann <humitos@gmail.com>
Date: Thu, 21 Dec 2017 17:44:33 -0500
Subject: [PATCH 06/12] Fix linting errors

---
 readthedocs/doc_builder/python_environments.py | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/readthedocs/doc_builder/python_environments.py b/readthedocs/doc_builder/python_environments.py
index adb5ee44eae..8cab79aa3d7 100644
--- a/readthedocs/doc_builder/python_environments.py
+++ b/readthedocs/doc_builder/python_environments.py
@@ -99,9 +99,7 @@ def venv_bin(self, filename=None):
         return os.path.join(*parts)
 
     def environment_json_path(self):
-        """
-        Return the path to the ``environment.json`` file for this venv.
-        """
+        """Return the path to the ``environment.json`` file for this venv."""
         return os.path.join(
             self.venv_path(),
             'environment.json',
@@ -137,7 +135,7 @@ def is_obsolete(self):
             return False
 
         # TODO: remove getattr when https://github.com/rtfd/readthedocs.org/pull/3339 got merged
-        build_image = getattr(self.config, 'build_image', self.version.project.container_image) or DOCKER_IMAGE
+        build_image = getattr(self.config, 'build_image', self.version.project.container_image) or DOCKER_IMAGE  # noqa
 
         # If the user define the Python version just as a major version
         # (e.g. ``2`` or ``3``) we won't know exactly which exact version was
@@ -149,11 +147,9 @@ def is_obsolete(self):
         ])
 
     def save_environment_json(self):
-        """
-        Save on disk Python and build image versions used to create the venv.
-        """
+        """Save on disk Python and build image versions used to create the venv."""
         # TODO: remove getattr when https://github.com/rtfd/readthedocs.org/pull/3339 got merged
-        build_image = getattr(self.config, 'build_image', self.version.project.container_image) or DOCKER_IMAGE
+        build_image = getattr(self.config, 'build_image', self.version.project.container_image) or DOCKER_IMAGE  # noqa
 
         data = {
             'python': {
@@ -167,7 +163,6 @@ def save_environment_json(self):
             json.dump(data, fpath)
 
 
-
 class Virtualenv(PythonEnvironment):
 
     """

From b7a4cc1089398ee6344decdb9f8ebf2135a8453d Mon Sep 17 00:00:00 2001
From: Manuel Kaufmann <humitos@gmail.com>
Date: Thu, 21 Dec 2017 19:55:15 -0500
Subject: [PATCH 07/12] Test cases for PythonEnvironment.is_obsolete

---
 .../doc_builder/python_environments.py        |   4 +-
 .../rtd_tests/tests/test_doc_building.py      | 111 +++++++++++++++++-
 2 files changed, 112 insertions(+), 3 deletions(-)

diff --git a/readthedocs/doc_builder/python_environments.py b/readthedocs/doc_builder/python_environments.py
index 8cab79aa3d7..343e29b5de2 100644
--- a/readthedocs/doc_builder/python_environments.py
+++ b/readthedocs/doc_builder/python_environments.py
@@ -8,7 +8,7 @@
 import logging
 import os
 import shutil
-from builtins import object
+from builtins import object, open
 
 from django.conf import settings
 
@@ -130,7 +130,7 @@ def is_obsolete(self):
                 environment_conf = json.load(fpath)
             env_python_version = environment_conf['python']['version']
             env_build_image = environment_conf['build']['image']
-        except (TypeError, KeyError, ValueError):
+        except (IOError, TypeError, KeyError, ValueError):
             log.error('Unable to read/parse environment.json file')
             return False
 
diff --git a/readthedocs/rtd_tests/tests/test_doc_building.py b/readthedocs/rtd_tests/tests/test_doc_building.py
index 818acaeb75a..cec2fe0c170 100644
--- a/readthedocs/rtd_tests/tests/test_doc_building.py
+++ b/readthedocs/rtd_tests/tests/test_doc_building.py
@@ -14,18 +14,22 @@
 from builtins import str
 
 import mock
+import pytest
 from django.test import TestCase
 from docker.errors import APIError as DockerAPIError
 from docker.errors import DockerException
-from mock import Mock, PropertyMock, patch
+from mock import Mock, PropertyMock, mock_open, patch
 
 from readthedocs.builds.constants import BUILD_STATE_CLONING
 from readthedocs.builds.models import Version
+from readthedocs.doc_builder.config import ConfigWrapper
 from readthedocs.doc_builder.environments import (
     BuildCommand, DockerBuildCommand, DockerEnvironment, LocalEnvironment)
 from readthedocs.doc_builder.exceptions import BuildEnvironmentError
+from readthedocs.doc_builder.python_environments import Virtualenv
 from readthedocs.projects.models import Project
 from readthedocs.rtd_tests.mocks.environment import EnvironmentMockGroup
+from readthedocs.rtd_tests.tests.test_config_wrapper import create_load
 
 DUMMY_BUILD_ID = 123
 SAMPLE_UNICODE = u'HérÉ îß sömê ünïçó∂é'
@@ -831,3 +835,108 @@ def test_command_oom_kill(self):
         self.assertEqual(
             str(cmd.output),
             u'Command killed due to excessive memory consumption\n')
+
+
+
+
+class TestAutoWipeEnvironment(TestCase):
+    fixtures = ['test_data']
+
+    def setUp(self):
+        self.pip = Project.objects.get(slug='pip')
+        self.version = self.pip.versions.get(slug='0.8')
+
+    def test_is_obsolete_without_env_json_file(self):
+        yaml_config = create_load()()[0]
+        config = ConfigWrapper(version=self.version, yaml_config=yaml_config)
+
+        with patch('os.path.exists') as exists:
+            exists.return_value = False
+            python_env = Virtualenv(
+                version=self.version,
+                build_env=None,
+                config=config,
+            )
+
+        self.assertFalse(python_env.is_obsolete)
+
+    def test_is_obsolete_with_invalid_env_json_file(self):
+        yaml_config = create_load()()[0]
+        config = ConfigWrapper(version=self.version, yaml_config=yaml_config)
+
+        with patch('os.path.exists') as exists:
+            exists.return_value = True
+            python_env = Virtualenv(
+                version=self.version,
+                build_env=None,
+                config=config,
+            )
+
+        self.assertFalse(python_env.is_obsolete)
+
+    def test_is_obsolete_with_json_different_python_version(self):
+        config_data = {
+            'build': {
+                'image': '2.0',
+            },
+            'python': {
+                'version': 2.7,
+            },
+        }
+        yaml_config = create_load(config_data)()[0]
+        config = ConfigWrapper(version=self.version, yaml_config=yaml_config)
+
+        python_env = Virtualenv(
+            version=self.version,
+            build_env=None,
+            config=config,
+        )
+        env_json_data = '{"build": {"image": "readthedocs/build:2.0"}, "python": {"version": 3.5}}'
+        with patch('os.path.exists') as exists, patch('readthedocs.doc_builder.python_environments.open', mock_open(read_data=env_json_data)) as _open:  # noqa
+            exists.return_value = True
+            self.assertTrue(python_env.is_obsolete)
+
+    @pytest.mark.xfail(reason='build.image is not being considered yet')
+    def test_is_obsolete_with_json_different_build_image(self):
+        config_data = {
+            'build': {
+                'image': 'latest',
+            },
+            'python': {
+                'version': 2.7,
+            },
+        }
+        yaml_config = create_load(config_data)()[0]
+        config = ConfigWrapper(version=self.version, yaml_config=yaml_config)
+
+        python_env = Virtualenv(
+            version=self.version,
+            build_env=None,
+            config=config,
+        )
+        env_json_data = '{"build": {"image": "readthedocs/build:2.0"}, "python": {"version": 2.7}}'
+        with patch('os.path.exists') as exists, patch('readthedocs.doc_builder.python_environments.open', mock_open(read_data=env_json_data)) as _open:  # noqa
+            exists.return_value = True
+            self.assertTrue(python_env.is_obsolete)
+
+    def test_is_obsolete_with_json_same_data_as_version(self):
+        config_data = {
+            'build': {
+                'image': '2.0',
+            },
+            'python': {
+                'version': 3.5,
+            },
+        }
+        yaml_config = create_load(config_data)()[0]
+        config = ConfigWrapper(version=self.version, yaml_config=yaml_config)
+
+        python_env = Virtualenv(
+            version=self.version,
+            build_env=None,
+            config=config,
+        )
+        env_json_data = '{"build": {"image": "readthedocs/build:2.0"}, "python": {"version": 3.5}}'
+        with patch('os.path.exists') as exists, patch('readthedocs.doc_builder.python_environments.open', mock_open(read_data=env_json_data)) as _open:  # noqa
+            exists.return_value = True
+            self.assertFalse(python_env.is_obsolete)

From 49ed94332e00ae7d93a47843400f8c53f4c1c932 Mon Sep 17 00:00:00 2001
From: Manuel Kaufmann <humitos@gmail.com>
Date: Fri, 22 Dec 2017 18:56:48 -0500
Subject: [PATCH 08/12] Comment fix

---
 readthedocs/doc_builder/python_environments.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/readthedocs/doc_builder/python_environments.py b/readthedocs/doc_builder/python_environments.py
index 343e29b5de2..473c18f0570 100644
--- a/readthedocs/doc_builder/python_environments.py
+++ b/readthedocs/doc_builder/python_environments.py
@@ -119,7 +119,7 @@ def is_obsolete(self):
 
         :rtype: bool
         """
-        # Always return True if we don't have information about what Python
+        # Always returns False if we don't have information about what Python
         # version/Docker image was used to create the venv as backward
         # compatibility.
         if not os.path.exists(self.environment_json_path()):

From da1fde31d1756cb3f2790f0f5c753c7c1c0cc595 Mon Sep 17 00:00:00 2001
From: Manuel Kaufmann <humitos@gmail.com>
Date: Fri, 22 Dec 2017 18:59:50 -0500
Subject: [PATCH 09/12] Rename environment file

---
 readthedocs/doc_builder/python_environments.py | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/readthedocs/doc_builder/python_environments.py b/readthedocs/doc_builder/python_environments.py
index 473c18f0570..d7886e514df 100644
--- a/readthedocs/doc_builder/python_environments.py
+++ b/readthedocs/doc_builder/python_environments.py
@@ -99,10 +99,10 @@ def venv_bin(self, filename=None):
         return os.path.join(*parts)
 
     def environment_json_path(self):
-        """Return the path to the ``environment.json`` file for this venv."""
+        """Return the path to the ``readthedocs-environment.json`` file."""
         return os.path.join(
             self.venv_path(),
-            'environment.json',
+            'readthedocs-environment.json',
         )
 
     @property
@@ -110,10 +110,10 @@ def is_obsolete(self):
         """
         Determine if the Python version of the venv obsolete.
 
-        It checks the the data stored at ``environment.json`` and compares it
-        against the Python version in the project version to be built and the
-        Docker image used to create the venv against the one in the project
-        version config.
+        It checks the the data stored at ``readthedocs-environment.json`` and
+        compares it against the Python version in the project version to be
+        built and the Docker image used to create the venv against the one in
+        the project version config.
 
         :returns: ``True`` when it's obsolete and ``False`` otherwise
 
@@ -131,7 +131,7 @@ def is_obsolete(self):
             env_python_version = environment_conf['python']['version']
             env_build_image = environment_conf['build']['image']
         except (IOError, TypeError, KeyError, ValueError):
-            log.error('Unable to read/parse environment.json file')
+            log.error('Unable to read/parse readthedocs-environment.json file')
             return False
 
         # TODO: remove getattr when https://github.com/rtfd/readthedocs.org/pull/3339 got merged

From 3b2f538cc218905bdc591d4b7d6ec6a9ad76dc82 Mon Sep 17 00:00:00 2001
From: Manuel Kaufmann <humitos@gmail.com>
Date: Wed, 27 Dec 2017 20:53:45 -0500
Subject: [PATCH 10/12] Make json.dump compatible with py2 and py3

---
 readthedocs/doc_builder/python_environments.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/readthedocs/doc_builder/python_environments.py b/readthedocs/doc_builder/python_environments.py
index d7886e514df..0e087e495ea 100644
--- a/readthedocs/doc_builder/python_environments.py
+++ b/readthedocs/doc_builder/python_environments.py
@@ -159,8 +159,11 @@ def save_environment_json(self):
                 'image': build_image,
             },
         }
+
         with open(self.environment_json_path(), 'w') as fpath:
-            json.dump(data, fpath)
+            # Compatibility for Py2 and Py3. ``io.TextIOWrapper`` expects
+            # unicode but ``json.dumps`` returns str in Py2.
+            fpath.write(unicode(json.dumps(data)))
 
 
 class Virtualenv(PythonEnvironment):

From a151cdeafaadc3f07eb36ee0ac7bbfedbf1439b8 Mon Sep 17 00:00:00 2001
From: Manuel Kaufmann <humitos@gmail.com>
Date: Wed, 27 Dec 2017 20:58:04 -0500
Subject: [PATCH 11/12] Use `config.python_full_version` instead of
 `config.python_version`

---
 readthedocs/doc_builder/config.py             | 25 +++++++++++--------
 .../doc_builder/python_environments.py        |  4 +--
 2 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/readthedocs/doc_builder/config.py b/readthedocs/doc_builder/config.py
index 2ce1db0ad9c..ae0fd84b99e 100644
--- a/readthedocs/doc_builder/config.py
+++ b/readthedocs/doc_builder/config.py
@@ -51,16 +51,7 @@ def extra_requirements(self):
 
     @property
     def python_interpreter(self):
-        ver = self.python_version
-        if ver in [2, 3]:
-            # Get the highest version of the major series version if user only
-            # gave us a version of '2', or '3'
-            ver = max(
-                list(
-                    filter(
-                        lambda x: x < ver + 1,
-                        self._yaml_config.get_valid_python_versions(),
-                    )))
+        ver = self.python_full_version
         return 'python{0}'.format(ver)
 
     @property
@@ -75,6 +66,20 @@ def python_version(self):
             version = 3
         return version
 
+    @property
+    def python_full_version(self):
+        ver = self.python_version
+        if ver in [2, 3]:
+            # Get the highest version of the major series version if user only
+            # gave us a version of '2', or '3'
+            ver = max(
+                list(
+                    filter(
+                        lambda x: x < ver + 1,
+                        self._yaml_config.get_valid_python_versions(),
+                    )))
+        return ver
+
     @property
     def use_system_site_packages(self):
         if 'use_system_site_packages' in self._yaml_config.get('python', {}):
diff --git a/readthedocs/doc_builder/python_environments.py b/readthedocs/doc_builder/python_environments.py
index 0e087e495ea..b64c8bbce35 100644
--- a/readthedocs/doc_builder/python_environments.py
+++ b/readthedocs/doc_builder/python_environments.py
@@ -142,7 +142,7 @@ def is_obsolete(self):
         # used to create the venv but we can still compare it against the new
         # one coming from the project version config.
         return any([
-            env_python_version != self.config.python_version,
+            env_python_version != self.config.python_full_version,
             env_build_image != build_image,
         ])
 
@@ -153,7 +153,7 @@ def save_environment_json(self):
 
         data = {
             'python': {
-                'version': self.config.python_version,
+                'version': self.config.python_full_version,
             },
             'build': {
                 'image': build_image,

From f31144a87df2e21c22932f5f3eee337fa9f69157 Mon Sep 17 00:00:00 2001
From: Manuel Kaufmann <humitos@gmail.com>
Date: Wed, 27 Dec 2017 21:12:43 -0500
Subject: [PATCH 12/12] Test for changing container_image at project level

---
 .../rtd_tests/tests/test_doc_building.py      | 26 +++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/readthedocs/rtd_tests/tests/test_doc_building.py b/readthedocs/rtd_tests/tests/test_doc_building.py
index cec2fe0c170..8e928d27dae 100644
--- a/readthedocs/rtd_tests/tests/test_doc_building.py
+++ b/readthedocs/rtd_tests/tests/test_doc_building.py
@@ -919,6 +919,32 @@ def test_is_obsolete_with_json_different_build_image(self):
             exists.return_value = True
             self.assertTrue(python_env.is_obsolete)
 
+    def test_is_obsolete_with_project_different_build_image(self):
+        config_data = {
+            'build': {
+                'image': '2.0',
+            },
+            'python': {
+                'version': 2.7,
+            },
+        }
+        yaml_config = create_load(config_data)()[0]
+        config = ConfigWrapper(version=self.version, yaml_config=yaml_config)
+
+        # Set container_image manually
+        self.pip.container_image = 'readthedocs/build:latest'
+        self.pip.save()
+
+        python_env = Virtualenv(
+            version=self.version,
+            build_env=None,
+            config=config,
+        )
+        env_json_data = '{"build": {"image": "readthedocs/build:2.0"}, "python": {"version": 2.7}}'
+        with patch('os.path.exists') as exists, patch('readthedocs.doc_builder.python_environments.open', mock_open(read_data=env_json_data)) as _open:  # noqa
+            exists.return_value = True
+            self.assertTrue(python_env.is_obsolete)
+
     def test_is_obsolete_with_json_same_data_as_version(self):
         config_data = {
             'build': {