Reuse test script wrapper in python gh action

Author: forus

.github/workflows/validate-python.yml

@@ -17,8 +17,4 @@ jobs:
           docker run -v ${PWD}:/cbioportal-core python:3.6 /bin/sh -c '
             cd cbioportal-core &&
             pip install -r requirements.txt &&
-            export PYTHONPATH=/cbioportal-core/scripts &&
-            cd tests/ &&
-            python unit_tests_validate_data.py &&
-            python system_tests_validate_data.py &&
-            python system_tests_validate_studies.py'
+            source test_scripts.sh'