[datafeed] don't allow arbitrary kwargs on DatafeedParser initializer else they will be handled nicely by appobject base class, while we rather want an error in the case of a source parser (arguable).

version=3
opts=uversionmangle=s/(rc|a|b|c)/~$1/ \
https://pypi.debian.net/cubicweb/cubicweb-(.+)\.(?:zip|tgz|tbz|txz|(?:tar\.(?:gz|bz2|xz)))