[test] Fix randomness in tests

[test] Drop unused import

[serverctl] allow to sync multiple and all sources in source-sync command Breaking change: by default source are not synced anymore if it is fresh (regards to synchronization-interval). To get the previous behavior an option --force is added. Closes #13886467

[tox] Split migractions tests from server environment These are the longest tests in this environment, so running them apart (in parallel of others) would hopefully speed up the whole suite.

[dataimport] Fix rdef loopup in importer

[py3k] left-over unicode() in authobjs.py

[server] Improve massive deletion of entities sqlserver is limited on the "IN" array size and produce an error "The query processor ran out of internal resources and could not produce a query plan". The exact limitation is unclear but can occur with > 10000 item in the array. See https://support.microsoft.com/en-us/kb/288095 Now we process the deletion by batch of 10000, some quick benchmarks show that there is no performance impact: delete_in(50000): 46.765182972 delete_in_batch(50000): 46.3242430687 delete_in(100000): 62.2969429493 delete_in_batch(100000): 61.8402349949

[hooks] Add a bunch of tests for session synchronization And change unicode into six.text_type in authobjs.py spotted by new tests.

[entities] Drop very old backward compat from erudi time (even the standard datetime type didn't exist at that time)

pep8 + docstrings and comments improvments