DOC: exclude autogenerated c/cpp/html files from 'trailing whitespace' checks
- [x] closes #24526 
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24549?src=pr&el=h1) Report
> Merging [#24549](https://codecov.io/gh/pandas-dev/pandas/pull/24549?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/179822a0a5b3e84c841bcb76e72a269d13cd3aad?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24549/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24549?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #24549   +/-   ##
=======================================
  Coverage   92.32%   92.32%           
=======================================
  Files         166      166           
  Lines       52455    52455           
=======================================
  Hits        48431    48431           
  Misses       4024     4024
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.75% <ø> (ø)` | :arrow_up: |
| #single | `43.01% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24549?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/24549?src=pr&el=footer). Last update [179822a...056b540](https://codecov.io/gh/pandas-dev/pandas/pull/24549?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/24549?src=pr&el=h1) Report
> Merging [#24549](https://codecov.io/gh/pandas-dev/pandas/pull/24549?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/e3b095074c5c3b29ec25a994cd204349b872d961?src=pr&el=desc) will **decrease** coverage by `0.03%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24549/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24549?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24549      +/-   ##
==========================================
- Coverage   92.37%   92.34%   -0.04%     
==========================================
  Files         166      166              
  Lines       52408    52310      -98     
==========================================
- Hits        48412    48304     -108     
- Misses       3996     4006      +10
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.77% <ø> (-0.02%)` | :arrow_down: |
| #single | `42.84% <ø> (-0.03%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24549?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/groupby/ops.py](https://codecov.io/gh/pandas-dev/pandas/pull/24549/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ3JvdXBieS9vcHMucHk=) | `94.15% <0%> (-2.58%)` | :arrow_down: |
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/24549/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `96.39% <0%> (-0.24%)` | :arrow_down: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/24549/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `87.94% <0%> (-0.19%)` | :arrow_down: |
| [pandas/core/groupby/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/24549/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ3JvdXBieS9nZW5lcmljLnB5) | `86.98% <0%> (-0.18%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/24549/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `96.65% <0%> (-0.16%)` | :arrow_down: |
| [pandas/core/internals/managers.py](https://codecov.io/gh/pandas-dev/pandas/pull/24549/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL21hbmFnZXJzLnB5) | `95.95% <0%> (-0.11%)` | :arrow_down: |
| [pandas/core/internals/blocks.py](https://codecov.io/gh/pandas-dev/pandas/pull/24549/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL2Jsb2Nrcy5weQ==) | `94.1% <0%> (-0.07%)` | :arrow_down: |
| [pandas/core/resample.py](https://codecov.io/gh/pandas-dev/pandas/pull/24549/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzYW1wbGUucHk=) | `97.22% <0%> (-0.02%)` | :arrow_down: |
| [pandas/core/panel.py](https://codecov.io/gh/pandas-dev/pandas/pull/24549/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcGFuZWwucHk=) | `97.9% <0%> (-0.01%)` | :arrow_down: |
| [pandas/core/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/24549/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYmFzZS5weQ==) | `97.75% <0%> (ø)` | :arrow_up: |
| ... and [3 more](https://codecov.io/gh/pandas-dev/pandas/pull/24549/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24549?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/24549?src=pr&el=footer). Last update [e3b0950...dcf5e04](https://codecov.io/gh/pandas-dev/pandas/pull/24549?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 so I think this helps. but this whole check is way too verbose, e.g. including .html, descends into the asv/envs directory, and includes things on the python path.

cc @datapythonista  @jreback - I did not understand the CI failure error. Seems unrelated to my changes. Should I just retry CI? @saurav2608 no, just leave this for @datapythonista to look. The CI failure is unrelated. There are C and C++ files in the pandas codebase, and I'd like to avoid tailing spaces on them too. Only the generated ones could be excluded.
```
./pandas/io/msgpack/_unpacker.cpp
./pandas/io/msgpack/_packer.cpp
./pandas/_libs/window.cpp
./pandas/util/move.c
./pandas/_libs/src/parser/io.c
./pandas/_libs/src/parser/tokenizer.c
./pandas/_libs/src/ujson/python/ujson.c
./pandas/_libs/src/ujson/python/objToJSON.c
./pandas/_libs/src/ujson/python/JSONtoObj.c
./pandas/_libs/src/ujson/lib/ultrajsondec.c
./pandas/_libs/src/ujson/lib/ultrajsonenc.c
./pandas/_libs/tslibs/src/datetime/np_datetime.c
./pandas/_libs/tslibs/src/datetime/np_datetime_strings.c
``` @saurav2608 can you address comments and merge master? > @saurav2608 can you address comments and merge master?

@datapythonista - I noticed that we are certain c/cpp files are linted [here](https://github.com/pandas-dev/pandas/blob/e3b095074c5c3b29ec25a994cd204349b872d961/ci/code_checks.sh#L95). 

The linter catches any trailing white spaces for the files in the specified folders.  
> * Add in you local environment (i.e. don't commit) tailing whitespaces to some file in `/pandas/io/msgpack` and see if the script (so the CI) fails in that case. I think so, but just to double check
> 
@datapythonista 
The cpp files are autogenerated - `./pandas/io/msgpack/_unpacker.cpp` Can you confirm that? The linter checks only .c and .h files. I can add cpp too if cpp files here are not autogenerated. 

 You're right. I fail to see what we are doing here then. This PR is to exclude the autogenerated .cpp files from the tailing whitespace check, and we're then fully linting them? > You're right. I fail to see what we are doing here then. This PR is to exclude the autogenerated .cpp files from the tailing whitespace check, and we're then fully linting them?

I have pushed the changes. The .c and .h files are fully Linted. I checked and trailing whitespace does show up as an error.  @jreback can you please merge this? i will look next day or 2 thanks @saurav2608 