Move tests/utils.py -> transformers/testing_utils.py (#5350)

tests/test_modeling_tf_gpt2.py

@@ -17,10 +17,10 @@
 import unittest
 
 from transformers import GPT2Config, is_tf_available
+from transformers.testing_utils import require_tf, slow
 
 from .test_configuration_common import ConfigTester
 from .test_modeling_tf_common import TFModelTesterMixin, ids_tensor
-from .utils import require_tf, slow
 
 
 if is_tf_available():