'Loads plugin using alias or class name
:param namespace: namespace where alias is defined
:param plugin_provider: plugin alias or class name
:returns: plugin that is loaded
:raises ImportError: if fails to load plugin'

@staticmethod
def load_class_for_provider(namespace, plugin_provider):

    try:
        return utils.load_class_by_alias_or_classname(namespace, plugin_provider)
    except ImportError:
        with excutils.save_and_reraise_exception():
            LOG.error(_LE("Plugin    '%s'    not    found."), plugin_provider)
