Name collision with backports package

[flimberger]

There is a naming collision with the backports package, which is used to bring features from newer Python releases to Python 2.
If such a package is installed (for example backports.ssl_match_hostname which is needed by websocket and in turn by docker-py), it results in the following error:

Extension error:
Could not import extension numfig (exception: cannot import name OrderedDict)

Possible workarounds are using a virtualenv without system site packages, or renaming the extensions/backports.py module (used in extensions/numfig.py:5) to something else.

[rddaz2013]

https://github.com/rddaz2013/sphinxtr/tree/UpdatePython27