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 _loadapp(self, proxy_config_path):
        """
        Load a proxy from an app.conf to get the memcache_ring

        :returns: the memcache_ring of the memcache middleware filter
        """
        with mock.patch('swift.proxy.server.Ring'):
            app = loadapp(proxy_config_path)
        memcache_ring = None
        while True:
            memcache_ring = getattr(app, 'memcache', None)
            if memcache_ring:
                break
            app = app.app
        return memcache_ring