'Get a single hook.
:param int hook_id: (required), id of the hook
:returns: :class:`Hook <github3.repos.hook.Hook>` if successful,
otherwise None'

@requires_auth
def hook(self, hook_id):

    json = None
    if (int(hook_id) > 0):
        url = self._build_url(u'hooks', str(hook_id), base_url=self._api)
        json = self._json(self._get(url), 200)
    return self._instance_or_null(Hook, json)
