Fix flake8 errors/warnings about import in cubicweb/_exceptions.py We either ignore errors in case of name re-exports and drop re-exports from old backwards compatibility. We fix the only occurrence of NoSelectableObject being imported from cubicweb in tests and update the import to use lgc instead.

[main]

cubicweb.session.secret = %(secret_1)s
cubicweb.auth.authtkt.session.secret = %(secret_2)s
cubicweb.auth.authtkt.persistent.secret = %(secret_3)s
cubicweb.auth.authtkt.session.secure = no
cubicweb.auth.authtkt.persistent.secure = no