Set sys.path properly for docs to build.

We used to do it this way, I'm not sure why it was changed.
Our settings files add directories to the path, so we need to
do it here so that names will be importable.

docs/source/conf.py

@@ -21,7 +21,17 @@ import os
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 # sys.path.insert(0, os.path.abspath('.'))
-sys.path.insert(0, os.path.abspath('../..'))  # mitx folder
+
+mitx = os.path.abspath('../..')
+
+sys.path.append(mitx)
+sys.path.append(os.path.join(mitx, "common/djangoapps"))
+sys.path.append(os.path.join(mitx, "common/lib"))
+sys.path.append(os.path.join(mitx, "common/lib/sandbox-packages"))
+sys.path.append(os.path.join(mitx, "lms/djangoapps"))
+sys.path.append(os.path.join(mitx, "lms/lib"))
+sys.path.append(os.path.join(mitx, "cms/djangoapps"))
+sys.path.append(os.path.join(mitx, "cms/lib"))
 
 #  django configuration  - careful here
 os.environ['DJANGO_SETTINGS_MODULE'] = 'lms.envs.test'