[test] Cleanup imports in unittest_form Remove unused and reorder, + use bare unittest along the way.

Fix log level parameter not taken into account in cwsource log table An error in the jquery selector of the html widget controlling the log level was the cause of this bug. Closes #15772634 (grafted from c9129aae884b476455c8ed1ad802efc3a26503a5)

[pyramid] Drop call to repository's start_looping_tasks method and warn about this We are about to drop the start_looping_tasks method and running "looping tasks" along the WSGI application is not a very good idea. So issue a warning pointing to the forthcoming "scheduler" command. Related to #17057223.

[test] Make unittest_serverctl.py flake8-clean

[wsgi] Drop calls to repo.start_looping_tasks It's unlikely that these implementations were ever used so we do not bother with deprecation or a warning. We just drop the call to this method which should not be called from within a WSGI application. Related to #17057223.

[pyramid] Drop useless "init_instance" module

[server] Drop inexistent "bootstrap" argument in Repository initialization This is a missing bit from 5de78b6fff2e. Unfortunately this code appears to be uncovered by our test suite.

[server] fix a typo in a docstring

[ctl] Load available configurations in "cubicweb-ctl list" Otherwise we rely on associated ctl plugins to be loaded which is arguably orthogonal to configurations.

[web/views] Fix a docstring