def coerce(cls, string):
        """Create a :class:`Requirement` object from a given package spec."""
        match = re.match(cls.spec_regex, string)
        if not match:
            raise InvalidRequirementSpecError("could not parse requirement")
        package = match.group(1)
        if all(match.group(2, 3)):
            version = "".join(match.group(2, 3))
        else:
            version = None
        return cls(package, version)
def _getProvenanceAfterMetadata(self, item, meta, user):
        resp = self.request(path='/item/%s/metadata' % item['_id'],
                            method='PUT', user=user, body=json.dumps(meta),
                            type='application/json')
        self.assertStatusOk(resp)
        return self._getProvenance(item, user)