Fix bad import with PyTorch <= 1.4.1 (#8237)

src/transformers/trainer_pt_utils.py

@@ -23,7 +23,7 @@ from typing import List, Optional, Union
 
 import numpy as np
 import torch
-from torch.optim.lr_scheduler import SAVE_STATE_WARNING
+from packaging import version
 from torch.utils.data.distributed import DistributedSampler
 from torch.utils.data.sampler import RandomSampler, Sampler
 
@@ -34,6 +34,11 @@ from .utils import logging
 if is_torch_tpu_available():
     import torch_xla.core.xla_model as xm
 
+if version.parse(torch.__version__) <= version.parse("1.4.1"):
+    SAVE_STATE_WARNING = ""
+else:
+    from torch.optim.lr_scheduler import SAVE_STATE_WARNING
+
 logger = logging.get_logger(__name__)