Skip tests properly (#31308)

* Skip tests properly

* [test_all]

* Add 'reason' as kwarg for skipTest

* [test_all] Fix up

* [test_all]

tests/models/fnet/test_tokenization_fnet.py

@@ -69,7 +69,7 @@ class FNetTokenizationTest(TokenizerTesterMixin, unittest.TestCase):
 
     def test_rust_and_python_full_tokenizers(self):
         if not self.test_rust_tokenizer:
-            return
+            self.skipTest(reason="test_rust_tokenizer is set to False")
 
         tokenizer = self.get_tokenizer()
         rust_tokenizer = self.get_rust_tokenizer()
@@ -194,7 +194,7 @@ class FNetTokenizationTest(TokenizerTesterMixin, unittest.TestCase):
     def test_padding(self, max_length=50):
         if not self.test_slow_tokenizer:
             # as we don't have a slow version, we can't compare the outputs between slow and fast versions
-            return
+            self.skipTest(reason="test_slow_tokenizer is set to False")
 
         for tokenizer, pretrained_name, kwargs in self.tokenizers_list:
             with self.subTest(f"{tokenizer.__class__.__name__} ({pretrained_name})"):