Remove redundant commas

[liuyan]

In glance source, there is redundant comma in front of parenthesis.
For example in below:

def _get_sort_key(self, req):
        """Parse a sort key query param from the request object."""
        sort_key = req.params.get('sort_key', 'created_at')
        if sort_key is not None and sort_key not in SUPPORTED_SORT_KEYS:
            _keys = ', '.join(SUPPORTED_SORT_KEYS)
            msg = _("Unsupported sort_key. Acceptable values: %s") % (_keys,)
            raise exc.HTTPBadRequest(explanation=msg)
        return sort_key

in line six, the commas behind "_keys" is redundant, so we should remove it .

[Ian Cordasco (icordasc)]

This more or less boils down to future-proofing. If we need to expand the parameters included in these messages, it reduces the visual noise in the diff.

[OpenStack Infra (hudson-openstack)]

Change abandoned by Glance Bot (<email address hidden>) on branch: master
Review: https://review.openstack.org/204618

[Cyril Roelandt (cyril-roelandt)]

$ git grep _get_sort_key
$

Marking as invalid