BLD: fix setup.py for xref #17798
xref #17798 
cc @TomAugspurger  Ah sorry about that. When you said "which IS picking this up", I thought you meant the setup.py was finding it, not that the test was correctly failing it. np # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17804?src=pr&el=h1) Report
> Merging [#17804](https://codecov.io/gh/pandas-dev/pandas/pull/17804?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/3b4121b5fca88a84bcc9dba56af568c8a2f901c0?src=pr&el=desc) will **decrease** coverage by `0.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17804/graphs/tree.svg?src=pr&token=eZ4WkYLtcO&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/17804?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17804      +/-   ##
==========================================
- Coverage   91.25%   91.23%   -0.02%     
==========================================
  Files         163      163              
  Lines       49971    49971              
==========================================
- Hits        45599    45590       -9     
- Misses       4372     4381       +9
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.03% <ø> (ø)` | :arrow_up: |
| #single | `40.24% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17804?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17804?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17804?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.74% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17804?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/17804?src=pr&el=footer). Last update [3b4121b...185b41d](https://codecov.io/gh/pandas-dev/pandas/pull/17804?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/17804?src=pr&el=h1) Report
> Merging [#17804](https://codecov.io/gh/pandas-dev/pandas/pull/17804?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/3b4121b5fca88a84bcc9dba56af568c8a2f901c0?src=pr&el=desc) will **decrease** coverage by `0.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17804/graphs/tree.svg?width=650&src=pr&token=eZ4WkYLtcO&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/17804?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17804      +/-   ##
==========================================
- Coverage   91.25%   91.23%   -0.02%     
==========================================
  Files         163      163              
  Lines       49971    49971              
==========================================
- Hits        45599    45590       -9     
- Misses       4372     4381       +9
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.03% <ø> (ø)` | :arrow_up: |
| #single | `40.24% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17804?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17804?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17804?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.74% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17804?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/17804?src=pr&el=footer). Last update [3b4121b...185b41d](https://codecov.io/gh/pandas-dev/pandas/pull/17804?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
