'Create a comment on a commit.
:param str body: (required), body of the message
:param str sha: (required), commit id
:param str path: (optional), relative path of the file to comment
on
:param str position: (optional), line index in the diff to comment on
:param int line: (optional), line number of the file to comment on,
default: 1
:returns: :class:`RepoComment <github3.repos.comment.RepoComment>` if
successful, otherwise None'

@requires_auth
def create_comment(self, body, sha, path=None, position=None, line=1):

    json = None
    if (body and sha and (line and (int(line) > 0))):
        data = {u'body': body, u'line': line, u'path': path, u'position': position}
        self._remove_none(data)
        url = self._build_url(u'commits', sha, u'comments', base_url=self._api)
        json = self._json(self._post(url, data=data), 201)
    return self._instance_or_null(RepoComment, json)
