[session] Allow self._open to be False in __enter__ I do not understand why this assertion was there in the first place. And currently, it makes running any migration impossible. Hopefully, someone may be able to explain. See also commit b48020a80dc3 which mentions this assertion and suggests to remove it.

#!/usr/bin/env python
from cubicweb.cwctl import run
import sys
run(sys.argv[1:])