Fail to load pre-trained tokens.
The PreTrainedTokenizer fails to load tokenizer files when I load tokenizer files from local tokenizer files.

The error is caused by code line 174 - 182 in [tokenization_utils.py](https://github.com/huggingface/pytorch-transformers/blob/master/pytorch_transformers/tokenization_utils.py). The code assumes that there are three tokenizer files: added_tokens.json, special_tokens_map.json, vocab.txt. However, these path of tokenizer files will be the same path if the given parameter "pretrained_model_name_or_path" is full path of "vocab.txt".
Hi, how do you solve this problem? If we set `pretrained_model_name_or_path` as a path to vocab.txt, it still need the two files: added_tokens.json, special_tokens_map.json. Where can we get these files? <|||||>> Hi, how do you solve this problem? If we set `pretrained_model_name_or_path` as a path to vocab.txt, it still need the two files: added_tokens.json, special_tokens_map.json. Where can we get these files?

You can ignore these files: added_tokens.json, special_tokens_map.json. All you need to do is to modify some code lines in the file: tokenization_utils.py. I have modified it in my forked repository as you can see [here](https://github.com/xijiz/pytorch-transformers/commit/31bc1ddf4f68ad790da9874a3623cf22d62dc186). <|||||>This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.
