stablerange: drop the cache on 'destroyed' if the repository have been strip, the cache is not usable as is. We could be smarter in the invalidation but that is a prototype anyway. G: changed hgext3rd/evolve/stablerange.py

# name space package to host third party extensions
from __future__ import absolute_import
import pkgutil
__path__ = pkgutil.extend_path(__path__, __name__)