BLD: since we already use setuptools, let's remove the optional logic…
… in setup.py (GH18113).

- [x] closes #18113 
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18448?src=pr&el=h1) Report
> Merging [#18448](https://codecov.io/gh/pandas-dev/pandas/pull/18448?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/c63435207375b172db9efdd0d31f32e0da555a72?src=pr&el=desc) will **decrease** coverage by `0.04%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/18448/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/18448?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #18448      +/-   ##
==========================================
- Coverage   91.35%   91.31%   -0.05%     
==========================================
  Files         163      163              
  Lines       49691    49691              
==========================================
- Hits        45397    45376      -21     
- Misses       4294     4315      +21
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.11% <ø> (-0.03%)` | :arrow_down: |
| #single | `39.67% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/18448?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/18448?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/18448?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `63.44% <0%> (-1.82%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/18448?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.8% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18448?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/18448?src=pr&el=footer). Last update [c634352...62254e5](https://codecov.io/gh/pandas-dev/pandas/pull/18448?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18448?src=pr&el=h1) Report
> Merging [#18448](https://codecov.io/gh/pandas-dev/pandas/pull/18448?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/0e168188811677f9de72a6a5b97253e551b6b04a?src=pr&el=desc) will **decrease** coverage by `0.15%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/18448/graphs/tree.svg?token=eZ4WkYLtcO&src=pr&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/18448?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #18448      +/-   ##
==========================================
- Coverage   91.46%   91.31%   -0.16%     
==========================================
  Files         157      163       +6     
  Lines       51439    49691    -1748     
==========================================
- Hits        47051    45376    -1675     
+ Misses       4388     4315      -73
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.11% <ø> (-0.21%)` | :arrow_down: |
| #single | `39.67% <ø> (-1.04%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/18448?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/computation/expressions.py](https://codecov.io/gh/pandas-dev/pandas/pull/18448/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tcHV0YXRpb24vZXhwcmVzc2lvbnMucHk=) | `0% <0%> (-94.96%)` | :arrow_down: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/18448/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/io/msgpack/\_version.py](https://codecov.io/gh/pandas-dev/pandas/pull/18448/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL21zZ3BhY2svX3ZlcnNpb24ucHk=) | `44.65% <0%> (-55.35%)` | :arrow_down: |
| [pandas/io/clipboard/clipboards.py](https://codecov.io/gh/pandas-dev/pandas/pull/18448/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2NsaXBib2FyZC9jbGlwYm9hcmRzLnB5) | `24.05% <0%> (-8.14%)` | :arrow_down: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/18448/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `63.44% <0%> (-1.82%)` | :arrow_down: |
| [pandas/core/indexes/interval.py](https://codecov.io/gh/pandas-dev/pandas/pull/18448/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9pbnRlcnZhbC5weQ==) | `92.52% <0%> (-0.53%)` | :arrow_down: |
| [pandas/core/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/18448/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYmFzZS5weQ==) | `96.56% <0%> (-0.21%)` | :arrow_down: |
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/18448/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `95.49% <0%> (-0.21%)` | :arrow_down: |
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/18448/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `95.73% <0%> (-0.18%)` | :arrow_down: |
| [pandas/core/reshape/merge.py](https://codecov.io/gh/pandas-dev/pandas/pull/18448/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9tZXJnZS5weQ==) | `94.26% <0%> (-0.15%)` | :arrow_down: |
| ... and [34 more](https://codecov.io/gh/pandas-dev/pandas/pull/18448/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18448?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/18448?src=pr&el=footer). Last update [0e16818...21cbe79](https://codecov.io/gh/pandas-dev/pandas/pull/18448?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 can you rebase and update Hello @gkonefal-reef! Thanks for updating the PR.

 - In the file [`setup.py`](https://github.com/pandas-dev/pandas/blob/21cbe794695bdee41527a02c01c59faa164dd467/setup.py), following are the PEP8 issues :

> [Line 47:80](https://github.com/pandas-dev/pandas/blob/21cbe794695bdee41527a02c01c59faa164dd467/setup.py#L47): [E501](https://duckduckgo.com/?q=pep8%20E501) line too long (82 > 79 characters)

 I've applied changes as it was requested. ok re-running on travis [here](https://github.com/jreback/pandas/commit/c6b88e11268500c8cc26e397d66c30e0853d5022) just to make sure thanks @gkonefal-reef 