The param comment for tag() in base.py mentions 0.1.5 and tags/0.1.5 as valid inputs, however the call to TagReference calls the inherited constructor (Reference in reference.py) with the default check_path=True, which returns a ValueError, if the tag/path given doesnt start with self._common_path_default + '/'.
Either the param comment needs to be adjusted or the tag parameter cleaned up so that it only returns the tag value to Reference.__init__.

