[datafeed] make cnxset handling of datafeed source more robust currently we may run in some cases where the session has no more cnxset depending on errors and parser's handling of the cnxset. Also, free the cnxset and reacquire it later, letting a chance to other threads to run.

don't use rset.rowcount in predicates, this makes them usable with other types such as lists

[c-c db-check] don't skip is/is_instance_of mandatory relation to avoid telling two opposite messages when the relation is missing. Closes #2465659

[ui tabs] avoid duplicate rset argument if already specified in tab kwargs. Closes #2464786

[entity edition] don't remove values from attribute cache on the repository side This follows changesets 552de9f0c46d, 1527b012802f, 25da1e5c7c50 and 4ba11607d84a. closes #2423719 ?

fix ldapuser test

Prepare 3.15.4

migration: replace empty passwords with random ones on upgrade

ldapuser2ldapfeed: create CWUsers with random passwords, not empty ones

[source/native] only system source users should be authenticated by the native source (closes #2465883)

[web test] fix test broken by 199fefe396ab

[fti] add some documentation

[form] add assertion to ensure field has a name when `role_name` is called

Added tag cubicweb-debian-version-3.15.3-1 for changeset 7ad423a5b6a8