Fix Roberta on TPU
Fixes #1569 
- Revert tf.print() to logger , since tf.print() is an unsupported TPU ops.
# [Codecov](https://codecov.io/gh/huggingface/transformers/pull/1570?src=pr&el=h1) Report
> Merging [#1570](https://codecov.io/gh/huggingface/transformers/pull/1570?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/transformers/commit/82f6abd98aaa691ca0adfe21e85a17dc6f386497?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/transformers/pull/1570/graphs/tree.svg?width=650&token=9qOlN6Hb1c&height=150&src=pr)](https://codecov.io/gh/huggingface/transformers/pull/1570?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master    #1570   +/-   ##
=======================================
  Coverage   86.16%   86.16%           
=======================================
  Files          91       91           
  Lines       13593    13593           
=======================================
  Hits        11713    11713           
  Misses       1880     1880
```


| [Impacted Files](https://codecov.io/gh/huggingface/transformers/pull/1570?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [transformers/modeling\_tf\_roberta.py](https://codecov.io/gh/huggingface/transformers/pull/1570/diff?src=pr&el=tree#diff-dHJhbnNmb3JtZXJzL21vZGVsaW5nX3RmX3JvYmVydGEucHk=) | `100% <100%> (ø)` | :arrow_up: |

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<|||||>Hum this situation is a bit annoying because we switched from `logger.error` to `tf.print` to solve #1350<|||||>Is there a specific reason why we have such a warning message for Roberta but not for other models? All models based on BERT are require the special tokens.
I was having the same issues as #1350 on my end using the logger (lots of zmq , operationnotallowed errors) . The solution for me was to remove the entire warning message altogether.
Is that viable in this scenario? <|||||>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.
