cubicweb #1993420 some junk remains in repository caches when an exception is raised during extid2eid [resolved]

and no rollback is done on the session.

prioritynormal
typebug
done in3.14.0
load0.200
load left0.000
closed by#99ae8c883ad3 [ms repository] when an exception is raised during extid2eid and no rollback is done, some manual cleanups have to be done (closes #1993420)