python: Provide support to select a valid python version.

- Update imports after wrapping the code.
- Fix python3 issues.
- Fix config path issues for in repo and install runs.

Closes #3537

tester/rt/coverage.py

@@ -47,7 +47,7 @@ from rtemstoolkit import execute
 from rtemstoolkit import macros
 
 
-from . import options
+import options
 
 class summary:
     def __init__(self, p_summary_dir):