Fixturize tests/frame/test_apply
Split off from #22730 as per review from @WillAyd 

Hello @h-vetinari! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/tests/frame/conftest.py`](https://github.com/h-vetinari/pandas/blob/0107e16d62c86df3567d6b8caf600f6a25263711/pandas/tests/frame/conftest.py) !

 - There are no PEP8 issues in the file [`pandas/tests/frame/test_apply.py`](https://github.com/h-vetinari/pandas/blob/0107e16d62c86df3567d6b8caf600f6a25263711/pandas/tests/frame/test_apply.py) !

 @gfyoung @jreback @WillAyd 
Could someone retrigger the failed travis job? Thanks. # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22735?src=pr&el=h1) Report
> Merging [#22735](https://codecov.io/gh/pandas-dev/pandas/pull/22735?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/1c113db60b68c5a262d64e92dc9de72bfe59aed5?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/22735/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/22735?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #22735      +/-   ##
==========================================
+ Coverage   92.17%   92.18%   +<.01%     
==========================================
  Files         169      169              
  Lines       50778    50815      +37     
==========================================
+ Hits        46807    46845      +38     
+ Misses       3971     3970       -1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.6% <ø> (ø)` | :arrow_up: |
| #single | `42.37% <ø> (+0.04%)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/22735?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/dtypes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/22735/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL2Jhc2UucHk=) | `100% <0%> (ø)` | :arrow_up: |
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/22735/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `96.67% <0%> (ø)` | :arrow_up: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/22735/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `86.03% <0%> (ø)` | :arrow_up: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/22735/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.2% <0%> (ø)` | :arrow_up: |
| [pandas/core/indexes/multi.py](https://codecov.io/gh/pandas-dev/pandas/pull/22735/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9tdWx0aS5weQ==) | `95.45% <0%> (ø)` | :arrow_up: |
| [pandas/io/formats/excel.py](https://codecov.io/gh/pandas-dev/pandas/pull/22735/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvZXhjZWwucHk=) | `97.4% <0%> (ø)` | :arrow_up: |
| [pandas/core/arrays/categorical.py](https://codecov.io/gh/pandas-dev/pandas/pull/22735/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2NhdGVnb3JpY2FsLnB5) | `95.75% <0%> (+0.01%)` | :arrow_up: |
| [pandas/core/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/22735/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYmFzZS5weQ==) | `97.61% <0%> (+0.01%)` | :arrow_up: |
| [pandas/core/indexes/datetimelike.py](https://codecov.io/gh/pandas-dev/pandas/pull/22735/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZWxpa2UucHk=) | `98.1% <0%> (+0.01%)` | :arrow_up: |
| [pandas/core/arrays/datetimelike.py](https://codecov.io/gh/pandas-dev/pandas/pull/22735/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2RhdGV0aW1lbGlrZS5weQ==) | `95.53% <0%> (+0.02%)` | :arrow_up: |
| ... and [5 more](https://codecov.io/gh/pandas-dev/pandas/pull/22735/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22735?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/22735?src=pr&el=footer). Last update [1c113db...77bcbce](https://codecov.io/gh/pandas-dev/pandas/pull/22735?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @WillAyd Green @WillAyd @gfyoung Green :) @h-vetinari i will look at all of the PRs soon lgtm. ping on green. @jreback @WillAyd @gfyoung Green. :) @h-vetinari : Thanks!