style: fix import format at pandas/tests/io/formats
- [ ] xref #23334 
- [x] passes `git diff master -u -- "*.py" | flake8 --diff`

Hello @streeck! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/tests/io/formats/test_css.py`](https://github.com/streeck/pandas/blob/d5d406dad84515ac1b8335dd73b1e57539ca6241/pandas/tests/io/formats/test_css.py) !

 - There are no PEP8 issues in the file [`pandas/tests/io/formats/test_eng_formatting.py`](https://github.com/streeck/pandas/blob/d5d406dad84515ac1b8335dd73b1e57539ca6241/pandas/tests/io/formats/test_eng_formatting.py) !

 - There are no PEP8 issues in the file [`pandas/tests/io/formats/test_format.py`](https://github.com/streeck/pandas/blob/d5d406dad84515ac1b8335dd73b1e57539ca6241/pandas/tests/io/formats/test_format.py) !

 - There are no PEP8 issues in the file [`pandas/tests/io/formats/test_printing.py`](https://github.com/streeck/pandas/blob/d5d406dad84515ac1b8335dd73b1e57539ca6241/pandas/tests/io/formats/test_printing.py) !

 - There are no PEP8 issues in the file [`pandas/tests/io/formats/test_style.py`](https://github.com/streeck/pandas/blob/d5d406dad84515ac1b8335dd73b1e57539ca6241/pandas/tests/io/formats/test_style.py) !

 - There are no PEP8 issues in the file [`pandas/tests/io/formats/test_to_csv.py`](https://github.com/streeck/pandas/blob/d5d406dad84515ac1b8335dd73b1e57539ca6241/pandas/tests/io/formats/test_to_csv.py) !

 - There are no PEP8 issues in the file [`pandas/tests/io/formats/test_to_excel.py`](https://github.com/streeck/pandas/blob/d5d406dad84515ac1b8335dd73b1e57539ca6241/pandas/tests/io/formats/test_to_excel.py) !

 - There are no PEP8 issues in the file [`pandas/tests/io/formats/test_to_html.py`](https://github.com/streeck/pandas/blob/d5d406dad84515ac1b8335dd73b1e57539ca6241/pandas/tests/io/formats/test_to_html.py) !

 - There are no PEP8 issues in the file [`pandas/tests/io/formats/test_to_latex.py`](https://github.com/streeck/pandas/blob/d5d406dad84515ac1b8335dd73b1e57539ca6241/pandas/tests/io/formats/test_to_latex.py) !

 can you merge master, we just updated the isort cfg can you merge master and update Will do later today # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23389?src=pr&el=h1) Report
> Merging [#23389](https://codecov.io/gh/pandas-dev/pandas/pull/23389?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/de39bfc5e5c6483cb2669773fa10ddc2e32ca111?src=pr&el=desc) will **increase** coverage by `0.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/23389/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/23389?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #23389      +/-   ##
==========================================
+ Coverage   92.21%   92.22%   +0.01%     
==========================================
  Files         161      169       +8     
  Lines       51173    51261      +88     
==========================================
+ Hits        47190    47277      +87     
- Misses       3983     3984       +1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.66% <ø> (+0.01%)` | :arrow_up: |
| #single | `42.23% <ø> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/23389?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/arrays/datetimelike.py](https://codecov.io/gh/pandas-dev/pandas/pull/23389/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2RhdGV0aW1lbGlrZS5weQ==) | `93.21% <0%> (-2.91%)` | :arrow_down: |
| [pandas/plotting/\_style.py](https://codecov.io/gh/pandas-dev/pandas/pull/23389/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19zdHlsZS5weQ==) | `75% <0%> (-2.42%)` | :arrow_down: |
| [pandas/core/arrays/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/23389/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2Jhc2UucHk=) | `97.35% <0%> (-0.67%)` | :arrow_down: |
| [pandas/core/arrays/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/23389/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2RhdGV0aW1lcy5weQ==) | `97.46% <0%> (-0.45%)` | :arrow_down: |
| [pandas/core/indexes/frozen.py](https://codecov.io/gh/pandas-dev/pandas/pull/23389/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9mcm96ZW4ucHk=) | `91.42% <0%> (-0.24%)` | :arrow_down: |
| [pandas/core/common.py](https://codecov.io/gh/pandas-dev/pandas/pull/23389/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tbW9uLnB5) | `98.34% <0%> (-0.08%)` | :arrow_down: |
| [pandas/io/packers.py](https://codecov.io/gh/pandas-dev/pandas/pull/23389/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3BhY2tlcnMucHk=) | `88.04% <0%> (-0.04%)` | :arrow_down: |
| [pandas/io/html.py](https://codecov.io/gh/pandas-dev/pandas/pull/23389/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2h0bWwucHk=) | `91.22% <0%> (-0.03%)` | :arrow_down: |
| [pandas/core/indexes/range.py](https://codecov.io/gh/pandas-dev/pandas/pull/23389/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9yYW5nZS5weQ==) | `95.77% <0%> (-0.03%)` | :arrow_down: |
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/23389/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `96.79% <0%> (-0.02%)` | :arrow_down: |
| ... and [52 more](https://codecov.io/gh/pandas-dev/pandas/pull/23389/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23389?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/pandas-dev/pandas/pull/23389?src=pr&el=footer). Last update [de39bfc...2430236](https://codecov.io/gh/pandas-dev/pandas/pull/23389?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Travis failure looks like it’s caused by missing jinja2.  Is there a viable solution to the importorskip? can you merge master and fixup @streeck pls merge master  Closing as stale, @streeck please let us know if you want to continue working on this.