[cwctl] on upgrade, clear instance_md5_version cache
The generate-static-datadir depends on a correct
config.instance_md5_version(), and we just invalidated it by
upgrading the instance.
.. _session_module:
:mod:`cubicweb.pyramid.session`
-------------------------------
.. automodule:: cubicweb.pyramid.session
.. autofunction:: includeme
.. autofunction:: CWSessionFactory