Just a heads up that the upcoming breaking change to WikiBase[1] will require a breaking change in how Pywikibot handles Quantities on Wikidata/WikiBase.
I have prepared a patch[2] which also ensures backwards compatibility for older WikiBase installations, but at the cost of more work for anyone wanting to use Pywikibot on Wikidata (and other up-to-date WikiBase installations).
The alternative is a more serious breakage for users running Pywikibot on older WikiBase installations but only a minor one for those running it on Wikidata.
[3]. The WikiBase breaking change goes live on Wikidata 2016-11-15