In run_xnli.py, output_dir seems to be used in place of tokenizer_name
# 🐛 Bug

## Information

I am trying to run the `run_xnli` example as found in the documentation. Unfortunately, I get a strange error were the script thinks the `output_dir` argument contains a model name.

It seems that `output_dir` has been used in place of `tokenizer_name` in some instances, such as this: `tokenizer = tokenizer_class.from_pretrained(args.output_dir, do_lower_case=args.do_lower_case)`

## To reproduce

Steps to reproduce the behavior:

1. Follow the example as found here: https://huggingface.co/transformers/examples.html#xnli

I get the following error:

```
Traceback (most recent call last):
  File "run_xnli.py", line 646, in <module>
    main()
  File "run_xnli.py", line 624, in main
    tokenizer = tokenizer_class.from_pretrained(args.output_dir, do_lower_case=args.do_lower_case)
  File "/mounts/Users/cisintern/antmarakis/anaconda3/lib/python3.7/site-packages/transformers/tokenization_utils.py", line 868, in from_pretrained
    return cls._from_pretrained(*inputs, **kwargs)
  File "/mounts/Users/cisintern/antmarakis/anaconda3/lib/python3.7/site-packages/transformers/tokenization_utils.py", line 971, in _from_pretrained
    list(cls.vocab_files_names.values()),
OSError: Model name '/tmp/debug_xnli/' was not found in tokenizers model name list (bert-base-uncased, bert-large-uncased, bert-base-cased, bert-large-cased, bert-base-multilingual-uncased, bert-base-multilingual-cased, bert-base-chinese, bert-base-german-cased, bert-large-uncased-whole-word-masking, bert-large-cased-whole-word-masking, bert-large-uncased-whole-word-masking-finetuned-squad, bert-large-cased-whole-word-masking-finetuned-squad, bert-base-cased-finetuned-mrpc, bert-base-german-dbmdz-cased, bert-base-german-dbmdz-uncased, bert-base-finnish-cased-v1, bert-base-finnish-uncased-v1, bert-base-dutch-cased). We assumed '/tmp/debug_xnli/' was a path, a model identifier, or url to a directory containing vocabulary files named ['vocab.txt'] but couldn't find such vocabulary files at this path or url.
```
Hello! Could you show us with which arguments to do you run the script?<|||||>Hi!

I am using the arguments as found in the Doc Example, except it is the uncased MultiBert, and the epochs are set to 1.0.

```
export XNLI_DIR=/path/to/XNLI

python run_xnli.py \
  --model_type bert \
  --model_name_or_path bert-base-multilingual-uncased \
  --language de \
  --train_language en \
  --do_train \
  --do_eval \
  --data_dir $XNLI_DIR \
  --per_gpu_train_batch_size 32 \
  --learning_rate 5e-5 \
  --num_train_epochs 1.0 \
  --max_seq_length 128 \
  --output_dir /tmp/debug_xnli/ \
  --save_steps -1
```<|||||>To be honest, someone should rewrite this script according to #3800 

In case you want to do it @antmarakis (we can help) 😊<|||||>Hi!

I am not sure if I could rewrite it right now, but I can make a start and others can then take it from there? I have already fixed the issue proposed here, I will get on refactoring the script next week if nobody else picks this up :).<|||||>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.
