def rpm_compare(self, a, b):
        """
        Compare rpm component version 'a' with 'b'.
        'name' is implied equal as it is the key() lookup
        """
        if a['version'] == b['version'] and \
           a['release'] == b['release'] and \
           a['signature'] == b['signature']:
            return

        raise ValueError("%s != %s" % (a, b))