[cleanup] Fix some flake8 errors

[test] Stop using lgc.testlib in unittest_migractions

[test] Drop no more used "maxeid" based deletion in BaseQuerierTC and derived tests This is probably only necessary for QuerierTC itself, move it there and drop incantation from other derived classes to deactivate this feature.

[rql2sql/test] Remove dead setUpModule tearDownModule they are overwritten a few lines below , hence this code is dead and not necessary for test success, drop it.