py3: fix formatting of LookupError for workingctx
Spotted while writing broken tests for "hg grep -fr'wdir()'".
basectx._fileinfo() raises ManifestLookupError(self._node, ..), but _node
of the workingctx is None for historical reasons.
# name space package to host third party extensions
from __future__ import absolute_import
import pkgutil
__path__ = pkgutil.extend_path(__path__, __name__)