Tests: fix some tests passing even if there are Python errors

Blender was not configured to exit with non-zero return code on Python errors.
A bunch of tests worked around this but not all. This removes the need for such
workarounds.

tests/python/bl_alembic_io_test.py

@@ -375,12 +375,4 @@ def main():
 
 
 if __name__ == "__main__":
-    import traceback
-    # So a python error exits Blender itself too
-    try:
-        main()
-    except SystemExit:
-        raise
-    except:
-        traceback.print_exc()
-        sys.exit(1)
+    main()