Merge pull request #1920 from jakirkham/pep8_e712_fix

STY: Fix PEP8 - E712 linting error (fixes tests)

Author: ericholscher

readthedocs/doc_builder/environments.py

@@ -450,7 +450,7 @@ def __enter__(self):
             # locking code, so we throw an exception.
             state = self.container_state()
             if state is not None:
-                if state.get('Running') == True:
+                if state.get('Running') is True:
                     exc = BuildEnvironmentError(
                         _('A build environment is currently '
                           'running for this version'))