read().splitlines() -> readlines()
splitlines() does not work as what we expect here for bert-base-chinese because there is a '\u2028' (unicode line seperator) token in vocab file. Value of '\u2028'.splitlines() is ['', ''].
Perhaps we should use readlines() instead.
# [Codecov](https://codecov.io/gh/huggingface/pytorch-transformers/pull/860?src=pr&el=h1) Report
> Merging [#860](https://codecov.io/gh/huggingface/pytorch-transformers/pull/860?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/pytorch-transformers/commit/2f869dc6651f9cf9253f4c5a43279027a0eccfc5?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/pytorch-transformers/pull/860/graphs/tree.svg?width=650&token=9qOlN6Hb1c&height=150&src=pr)](https://codecov.io/gh/huggingface/pytorch-transformers/pull/860?src=pr&el=tree)

```diff
@@          Coverage Diff           @@
##           master    #860   +/-   ##
======================================
  Coverage    78.9%   78.9%           
======================================
  Files          34      34           
  Lines        6192    6192           
======================================
  Hits         4886    4886           
  Misses       1306    1306
```


| [Impacted Files](https://codecov.io/gh/huggingface/pytorch-transformers/pull/860?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pytorch\_transformers/tokenization\_bert.py](https://codecov.io/gh/huggingface/pytorch-transformers/pull/860/diff?src=pr&el=tree#diff-cHl0b3JjaF90cmFuc2Zvcm1lcnMvdG9rZW5pemF0aW9uX2JlcnQucHk=) | `93.2% <100%> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/huggingface/pytorch-transformers/pull/860?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/huggingface/pytorch-transformers/pull/860?src=pr&el=footer). Last update [2f869dc...bef0c62](https://codecov.io/gh/huggingface/pytorch-transformers/pull/860?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
<|||||>Great, thanks!