Fix yaml_cantera2Test mock RMG object missing verbose_comments attribute.

There's a mock RMG object that was missing the attribute, which
caused an error in the unit tests.

Author: rwest

test/rmgpy/yaml_cantera2Test.py

@@ -243,6 +243,7 @@ def __init__(self, out_dir):
                 self.output_directory = out_dir
                 self.reaction_model = MockModel()
                 self.save_edge_species = False
+                self.verbose_comments = False
 
         mock_rmg = MockRMG(self.tmp_dir)
         save_cantera_files(mock_rmg)
@@ -401,6 +402,7 @@ def __init__(self, out_dir, model):
                 self.output_directory = out_dir
                 self.reaction_model = model
                 self.save_edge_species = False
+                self.verbose_comments = False
 
         return MockRMG(self.tmp_dir, MockModel(MockCore(species_list, reaction_list)))