GaudiKernel: migrate tests to pytest and various fixes

Migrate the GaudiKernel python tests from nose to pytest (they were already running as pytest but with several deprecation warnings).

In addition extend test_Configurables to cover more use-cases (in preparation for !1503 (merged)):

• Fix the cleanup function
• Extend the test to dict and list properties
• Migrate to pytest fixtures and exception handling

changed milestone to %v37r2

added 3 commits

• 9909311d - GaudiKernel: fix and extend test_Configurables
• adb4274a - GaudiKernel: migrate test_instructionsetLevel to pytest
• a14dbd07 - GaudiKernel: rename nose test directory to pytest

Compare with previous version

@clemenci, in order to address your comments on !1503 (merged) I wanted to get the tests in better shape before extending them. Maybe we can get this merged before I continue on the other MR.

approved this merge request

Thanks for the clean up.

merged

mentioned in commit b9abf6ff