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_blendfile_liblink.py

@@ -75,9 +75,4 @@ def main():
 if __name__ == '__main__':
     import sys
     sys.argv = [__file__] + (sys.argv[sys.argv.index("--") + 1:] if "--" in sys.argv else [])
-    try:
-        main()
-    except:
-        import traceback
-        traceback.print_exc()
-        sys.exit(1)
+    main()