[test] Add a "version" to cubicweb_mycube/__pkginfo__.py Starting from Python 3.5, unittest_cwctl.py::CubicWebCtlTC.test_list() would fail without this.

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