Update launch/test/launch/substitutions/test_python_expression.py

Co-authored-by: Chris Lalancette <[email protected]>

launch/test/launch/substitutions/test_python_expression.py

@@ -134,7 +134,7 @@ def test_python_substitution_submodule():
     try:
         result = subst.perform(lc)
     except SubstitutionFailure:
-        pytest.fail('Failed to evaluate PythonExpression containing sys module.')
+        pytest.fail('Failed to evaluate PythonExpression containing submodules.')
 
     # The expression should evaluate to True
     assert result