[ck2yaml] Raise the error when ck2yaml accidentally writes element

symbol string which includes number in it, issue Cantera#853

interfaces/cython/cantera/ck2yaml.py

@@ -865,7 +865,15 @@ def read_NASA7_entry(self, lines, TintDefault, comments):
         if not composition:
             raise InputError("Error parsing elemental composition for "
                              "species '{}'", species)
-
+        else:
+            for symbol in composition.keys():
+
+                # check if self.parse_composition parses composition correctly
+                if any(map(str.isdigit, symbol)) and symbol not in self.elements:
+                    raise InputError("Error parsing elemental composition for "
+                                     "species thermo entry\n{}"
+                                     "\n the first line has an incorrect format", "".join(lines))
+
         # Extract the NASA polynomial coefficients
         # Remember that the high-T polynomial comes first!
         Tmin = fortFloat(lines[0][45:55])

interfaces/cython/cantera/test/test_convert.py

@@ -468,7 +468,10 @@ def test_extra(self):
         self.assertEqual(desc, 'This is an alternative description.')
         for key in ['foo', 'bar']:
             self.assertIn(key, yml.keys())
-
+
+    def test_error_for_big_element_number(self):
+        with self.assertRaisesRegex(self.InputError, 'the first line has an incorrect format'):
+            self.convert('big_element_num_err.inp')
 
 class CtmlConverterTest(utilities.CanteraTest):
     def test_sofc(self):