'Get a single commit comment.
:param int comment_id: (required), id of the comment used by GitHub
:returns: :class:`RepoComment <github3.repos.comment.RepoComment>` if
successful, otherwise None'

def commit_comment(self, comment_id):

    url = self._build_url(u'comments', str(comment_id), base_url=self._api)
    json = self._json(self._get(url), 200)
    return self._instance_or_null(RepoComment, json)
