Make Sphinx to share environment between commands

Remove the `-E` from Sphinx command so it can shares the saved environment
between commands from the same build.

This will speed up a little those builds that are building multiple formats.

Closes #10701

Author: humitos

readthedocs/doc_builder/backends/sphinx.py

@@ -295,7 +295,6 @@ def build(self):
         build_command = [
             *self.get_sphinx_cmd(),
             "-T",
-            "-E",
         ]
         if self.config.sphinx.fail_on_warning:
             build_command.extend(["-W", "--keep-going"])
@@ -483,7 +482,6 @@ def build(self):
         self.run(
             *self.get_sphinx_cmd(),
             "-T",
-            "-E",
             "-b",
             self.sphinx_builder,
             "-d",

readthedocs/projects/tests/test_build_tasks.py

@@ -191,7 +191,6 @@ def test_build_sphinx_formats(self, load_yaml_config, formats, builders):
                 "-m",
                 "sphinx",
                 "-T",
-                "-E",
                 "-b",
                 "html",
                 "-d",
@@ -212,7 +211,6 @@ def test_build_sphinx_formats(self, load_yaml_config, formats, builders):
                     "-m",
                     "sphinx",
                     "-T",
-                    "-E",
                     "-b",
                     builder,
                     "-d",
@@ -829,7 +827,6 @@ def test_build_commands_executed(
                     "-m",
                     "sphinx",
                     "-T",
-                    "-E",
                     "-b",
                     "html",
                     "-d",
@@ -846,7 +843,6 @@ def test_build_commands_executed(
                     "-m",
                     "sphinx",
                     "-T",
-                    "-E",
                     "-b",
                     "readthedocssinglehtmllocalmedia",
                     "-d",
@@ -891,7 +887,6 @@ def test_build_commands_executed(
                     "-m",
                     "sphinx",
                     "-T",
-                    "-E",
                     "-b",
                     "latex",
                     "-d",
@@ -911,7 +906,6 @@ def test_build_commands_executed(
                     "-m",
                     "sphinx",
                     "-T",
-                    "-E",
                     "-b",
                     "epub",
                     "-d",
@@ -1467,7 +1461,6 @@ def test_sphinx_normalized_language(self, load_yaml_config):
                     "-m",
                     "sphinx",
                     "-T",
-                    "-E",
                     "-W",  # fail on warning flag
                     "--keep-going",  # fail on warning flag
                     "-b",
@@ -1506,7 +1499,6 @@ def test_sphinx_fail_on_warning(self, load_yaml_config):
                     "-m",
                     "sphinx",
                     "-T",
-                    "-E",
                     "-W",  # fail on warning flag
                     "--keep-going",  # fail on warning flag
                     "-b",
@@ -1843,7 +1835,6 @@ def test_sphinx_builder(self, load_yaml_config, value, command):
                     "-m",
                     "sphinx",
                     "-T",
-                    "-E",
                     "-b",
                     command,
                     "-d",