TST: xref #25630
skip on PY2 & old numpy for masked arrays

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25643?src=pr&el=h1) Report
> :exclamation: No coverage uploaded for pull request base (`master@16edaaf`). [Click here to learn what that means](https://docs.codecov.io/docs/error-reference#section-missing-base-commit).
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25643/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25643?src=pr&el=tree)

```diff
@@            Coverage Diff            @@
##             master   #25643   +/-   ##
=========================================
  Coverage          ?   41.71%           
=========================================
  Files             ?      173           
  Lines             ?    52968           
  Branches          ?        0           
=========================================
  Hits              ?    22096           
  Misses            ?    30872           
  Partials          ?        0
```

| Flag | Coverage Δ | |
|---|---|---|
| #single | `41.71% <ø> (?)` | |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25643?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/25643?src=pr&el=footer). Last update [16edaaf...51f048a](https://codecov.io/gh/pandas-dev/pandas/pull/25643?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/25643?src=pr&el=h1) Report
> Merging [#25643](https://codecov.io/gh/pandas-dev/pandas/pull/25643?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/16edaaf756ce0b3b1d5ab74ca754a9ccd774825a?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/25643/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25643?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #25643   +/-   ##
=======================================
  Coverage   91.26%   91.26%           
=======================================
  Files         173      173           
  Lines       52968    52968           
=======================================
  Hits        48339    48339           
  Misses       4629     4629
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.83% <ø> (ø)` | :arrow_up: |
| #single | `41.71% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25643?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/25643?src=pr&el=footer). Last update [16edaaf...51f048a](https://codecov.io/gh/pandas-dev/pandas/pull/25643?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

```
$ git checkout 0.24.x
$ git pull
```

2. Cherry pick the first parent branch of the this PR on top of the older branch:
```
$ git cherry-pick -m1 f88613929d6c83952cb5a6bf70678a78be480baa
```

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

```
$ git commit -am 'Backport PR #25643: TST: xref #25630'
```

4. Push to a named branch :

```
git push YOURFORK 0.24.x:auto-backport-of-pr-25643-on-0.24.x
```

5. Create a PR against branch 0.24.x, I would have named this PR:

> "Backport PR #25643 on branch 0.24.x"

And apply the correct labels and milestones.

Congratulation you did some good work ! Hopefully your backport PR will be tested by the continuous integration and merged soon!

If these instruction are inaccurate, feel free to [suggest an improvement](https://github.com/MeeseeksBox/MeeseeksDev).
                