Print test comments when external tests fail

Makes it easier to locate the failing tests in the test file

ext_tests.py

@@ -60,12 +60,15 @@ class TestCaseTemplate(unittest.TestCase):
                 )
 
         else:
-            res = jsonpatch.apply_patch(test['doc'], test['patch'])
+            try:
+                res = jsonpatch.apply_patch(test['doc'], test['patch'])
+            except jsonpatch.JsonPatchException as jpe:
+                raise Exception(test.get('comment', '')) from jpe
 
             # if there is no 'expected' we only verify that applying the patch
             # does not raies an exception
             if 'expected' in test:
-                self.assertEquals(res, test['expected'])
+                self.assertEquals(res, test['expected'], test.get('comment', ''))
 
 
 def make_test_case(tests):