POC: linting cython files
The edits in indexing.pyx are just to get the linting to pass for demonstration purposes.

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24872?src=pr&el=h1) Report
> Merging [#24872](https://codecov.io/gh/pandas-dev/pandas/pull/24872?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/12bb6d0536b947f74b66ebe18b5f451bfdd7453f?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/24872/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24872?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #24872   +/-   ##
=======================================
  Coverage   92.38%   92.38%           
=======================================
  Files         166      166           
  Lines       52412    52412           
=======================================
  Hits        48423    48423           
  Misses       3989     3989
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.81% <ø> (ø)` | :arrow_up: |
| #single | `42.89% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24872?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/24872?src=pr&el=footer). Last update [12bb6d0...8c7a753](https://codecov.io/gh/pandas-dev/pandas/pull/24872?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/24872?src=pr&el=h1) Report
> Merging [#24872](https://codecov.io/gh/pandas-dev/pandas/pull/24872?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/12bb6d0536b947f74b66ebe18b5f451bfdd7453f?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24872/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24872?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24872      +/-   ##
==========================================
- Coverage   92.38%   92.38%   -0.01%     
==========================================
  Files         166      166              
  Lines       52412    52410       -2     
==========================================
- Hits        48423    48421       -2     
  Misses       3989     3989
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.81% <ø> (-0.01%)` | :arrow_down: |
| #single | `42.89% <ø> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24872?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/reshape/util.py](https://codecov.io/gh/pandas-dev/pandas/pull/24872/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS91dGlsLnB5) | `100% <0%> (ø)` | :arrow_up: |
| [pandas/core/computation/expr.py](https://codecov.io/gh/pandas-dev/pandas/pull/24872/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tcHV0YXRpb24vZXhwci5weQ==) | `88.68% <0%> (+0.11%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24872?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/24872?src=pr&el=footer). Last update [12bb6d0...45d5d1c](https://codecov.io/gh/pandas-dev/pandas/pull/24872?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Hello @jbrockmendel! Thanks for updating the PR.



Cheers ! There are no PEP8 issues in this Pull Request. :beers: 

##### Comment last updated on January 22, 2019 at 17:33 Hours UTC