There is currently no test instance for Commons available through pywikibot making testing of Commons related code (especially upload) problematic.
AFAIK http://commons.wikimedia.beta.wmflabs.org is the designated test site for Commons. So adding this to the families would be nice.
Two things makes this more complicated:
- the domain is not the same as that for commons.wikimedia.org (so I'm not sure it can simply be added as a language in commons_family.py)
- beta commons does not (yet) support https (T50501)