[server/test] Add an assertion in test_statement_timeout

[datafeed] minor cleanups to cwxml parser

[datafeed] don't allow arbitrary kwargs on DatafeedParser initializer else they will be handled nicely by appobject base class, while we rather want an error in the case of a source parser (arguable).

[datafeed] gives information about moved entities to the parser Also, don't support anymore arbitrary parameters at parser initialization. Related to #5414754

[datafeed] simplify SQL query used to retrieve information about entities from an external source no need to join on cw_source

[datafeed] rename parser.sourceuris to source_uris Its more readable. Also, uniformize related method and local identifier names.

[datafeed] move process_urls to the parser

[tox] Use py.test to run tests In unittest_rqlrewrite.py and repotest.py, rename utility functions so that they are not considered as "test functions" by py.test.

[test] Fix devtools unittest_i18n when ran without pytest There is currently some weird error, requiring both to hack cubicweb.__path__ and to stop using load_module_from_name to load the registry. Introduce a dependency on to-be-released version of logilab common integrating fix for https://www.logilab.org/ticket/6085650 Do some extra import cleanups along the way.

[server] explicitly set postgres LC_MESSAGES variable to C on connection We parse some error messages so we need them to be in English. It's not clear to me exactly when that's not the case, but this fixes running unittest_postgres' "test_constraint_validationerror" with py.test for Sylvain.