Add test to check that error messages from ctml_writer are propagated

interfaces/cython/cantera/test/test_convert.py

@@ -324,3 +324,11 @@ class CtmlConverterTest(utilities.CanteraTest):
     def test_pdep(self):
         gas = ct.Solution('../data/pdep-test.cti')
         self.assertEqual(gas.n_reactions, 6)
+
+    def test_invalid(self):
+        try:
+            gas = ct.Solution('../data/invalid.cti')
+        except RuntimeError as e:
+            err = e
+
+        self.assertIn('Multiply-declared species', err.args[0])

test/data/invalid.cti

@@ -0,0 +1,6 @@
+ideal_gas(
+    name="complete",
+    elements=" C H O",
+    species="gri30: O2 CH4 H2O CO2 CH4",
+    initial_state=state(temperature=298.0,
+                        pressure = 100000.0))