TST: remove some more warnings
TST: parametrize stata tests

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17645?src=pr&el=h1) Report
> Merging [#17645](https://codecov.io/gh/pandas-dev/pandas/pull/17645?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/85a10671f814301be3e0f3c24c2863488ec27ddd?src=pr&el=desc) will **increase** coverage by `0.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17645/graphs/tree.svg?src=pr&token=eZ4WkYLtcO&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/17645?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17645      +/-   ##
==========================================
+ Coverage   91.22%   91.24%   +0.01%     
==========================================
  Files         163      163              
  Lines       49661    49660       -1     
==========================================
+ Hits        45303    45311       +8     
+ Misses       4358     4349       -9
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.03% <100%> (+0.03%)` | :arrow_up: |
| #single | `40.17% <28.57%> (-0.06%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17645?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/17645?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `100% <ø> (ø)` | :arrow_up: |
| [pandas/core/dtypes/missing.py](https://codecov.io/gh/pandas-dev/pandas/pull/17645?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL21pc3NpbmcucHk=) | `90.44% <100%> (+3.25%)` | :arrow_up: |
| [pandas/core/internals.py](https://codecov.io/gh/pandas-dev/pandas/pull/17645?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzLnB5) | `94.31% <100%> (+0.01%)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17645?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17645?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.77% <0%> (-0.1%)` | :arrow_down: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/17645?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `65.2% <0%> (+1.81%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17645?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/17645?src=pr&el=footer). Last update [85a1067...e61bada](https://codecov.io/gh/pandas-dev/pandas/pull/17645?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @jreback : While we can, might as well correct "moar" to "more" in your commit message. 😄 