Create a module to split test case collection from checks

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/scripts/check_test_cases.py b/tests/scripts/check_test_cases.py
index 6809dd5..a7ad9ae 100755
--- a/tests/scripts/check_test_cases.py
+++ b/tests/scripts/check_test_cases.py
@@ -18,6 +18,7 @@
 
 import scripts_path # pylint: disable=unused-import
 from mbedtls_framework import build_tree
+import collect_test_cases
 
 class ScriptOutputError(ValueError):
     """A kind of ValueError that indicates we found