use deterministic order for updated env vars (#196)

Signed-off-by: Dirk Thomas <dirk-thomas@users.noreply.github.com>

ament_cmake_test/ament_cmake_test/__init__.py

@@ -150,7 +150,7 @@ def log(msg, **kwargs):
                 env[key] = value
                 updated_env_keys.add(key)
                 previous_key = key
-            for key in updated_env_keys:
+            for key in sorted(updated_env_keys):
                 log(' - {0}={1}'.format(key, env[key]))
         if args.append_env:
             log('-- run_test.py: extra environment variables to append:')