Fix environment.validate() being called without branch name.
Fix environment.validate() being called without branch name.

michaelclelland/documentation-generator,stweil/documentation-generator,cfengine/documentation-generator,michaelclelland/documentation-generator,stweil/documentation-generator,nickanderson/documentation-generator,nickanderson/documentation-generator,michaelclelland/documentation-generator,stweil/documentation-generator,michaelclelland/documentation-generator,stweil/documentation-generator,cfengine/documentation-generator,michaelclelland/documentation-generator,stweil/documentation-generator,nickanderson/documentation-generator,nickanderson/documentation-generator,nickanderson/documentation-generator,cfengine/documentation-generator,cfengine/documentation-generator,cfengine/documentation-generator