[server] Remove pseudo-handling of exceptions in Repository._delete_cascade_multi() It seems to me that we never want to pass on an exception here be it in "test" mode or not, so remove the last `except Exception:` clause. For instance, the actual implementation would pass on an IntegrityError and thus possibly hide it in a log message. Concerning the `except Unauthorized:`, as said by the log message this should not happen because we are within a `security_enabled(write=False)` context. So remove it as well. As far as I can tell, this strange handling of exceptions dates from 37668bf302f5 and there is no clear justification to it.

[web] fix os.rename usage on windows when destination exists os.rename on windows will raise OSError (or WindowsError subclass) when if destination file already exists. Also check that exception is EEXIST. There is an attempt to fix in f6ba947c but using IOError instead of OSError. Closes #14214794

[skeleton] Add "cubicweb.session.secret" to development.ini Commented as other "secret" settings. At least, now all settings are present in the development.ini file. [ci skip]