https://bugzilla.redhat.com/show_bug.cgi?id=1219288
--- Comment #11 from Miroslav Suchý msuchy@redhat.com --- Both https://pypi.python.org/pypi/marshmallow http://marshmallow.readthedocs.org/en/latest/ state 2.0.0b5 as release. I do not know what "b" stands for. For me - it is released, then it is release number. I won't judge the upstream for the numbering.
However if this is blocker for you I can put the short git hash in Release number.