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

GaudiKernel/tests/pytest/test_Configurables.py

@@ -8,12 +8,12 @@
 # granted to it by virtue of its status as an Intergovernmental Organization        #
 # or submit itself to any jurisdiction.                                             #
 #####################################################################################
-# Prepare dummy configurables
+import pytest
 from GaudiKernel.Configurable import Configurable, ConfigurableAlgorithm
 from GaudiKernel.DataHandle import DataHandle
-import pytest
 
 
+# Prepare dummy configurables
 class MyAlg(ConfigurableAlgorithm):
     __slots__ = {
         "Text": "some text",