Alias ugettext to gettext method of cwGNUTranslations in Python 3
The former does not exist in Python 3, but we rely on it.
This fixes test_login_bad_password in cubicweb/pyramid/test/test_login.py
which has never passed since being introduced in 6392f34fcdad.
usr/lib/python2*/*-packages/cubicweb/entities/
usr/lib/python2*/*-packages/cubicweb/ext/
usr/share/cubicweb/cubes/
usr/lib/python2*/*-packages/cubicweb/*.py