[ssplanner] Prevent execution of write queries involving computed relations Previously, setting a computed relation upon entity creation or modification (using the ORM or an RQL query) would usually fail with an operational error in the backend ("no such table"). However, under some mysterious circumstances (like passing a string as value in cw_set for a computed relation), the RQL to SQL transformation would simply drop the clause. To prevent this to happen, we add a check for computed relation before adding a relation to an execution plan. This check raises a QueryError. It happens in several places: * in querier.InsertPlan.add_relation_def() (called from several places in ssplanner steps) for INSERT queries, * in ssplanner.UpdateStep.execute() for SET queries and, * in ssplanner.SSplanner.build_delete_plan() for DELETE queries. Tests added to unittest_querier.py because unittest_sslplanner.py looked inappropriate (it has only unit tests) and the former already had a NonRegressionTC class.

[querier] Expand 'rdef' argument in InsertPlan.add_relation_def() Expand the 'rdef' tuple to improve readability. The 'rtype' value is not used at the moment, but will in the next changeset.

[server] Use dict.setdefault() instead of if/else in repo.glob_add_relations()

[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.

[rql2sql/test] Move base class from repotest to unittest_rql2sql It's only used there, so move it closer to its usage. Along the way, stop using lgc.testlib.

[rql2sql/test] Set maxDiff to None to see full diffs this is usually useful to compare SQL strings

[rql2sql] Use string_type instead of unicode for py3k support