Support hard-masked numpy arrays
State: closed

- [x] closes #24574
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

For the whatsnew entry, is this reasonable?
```rst
- :func:`DataFrame` and :func:`Series` now properly handle 
numpy masked arrays with hardened masks. Previously, constructing 
a DataFrame or Series from a masked array with a hard mask would 
create a pandas object containing the underlying value, rather than the
expected NaN. (:issue:`24574`)
```

Labels:
name: Bug
name: Reshaping
description: Concat, Merge/Join, Stack/Unstack, Explode

Comments:
Hello @karldw! Thanks for updating the PR.





 - In the file [`pandas/tests/frame/test_constructors.py`](https://github.com/pandas-dev/pandas/blob/3ff25bdfcc63812afb0288afb12c3720e7b3cdce/pandas/tests/frame/test_constructors.py), following are the PEP8 issues :

> [Line 767:13](https://github.com/pandas-dev/pandas/blob/3ff25bdfcc63812afb0288afb12c3720e7b3cdce/pandas/tests/frame/test_constructors.py#L767): [E123](https://duckduckgo.com/?q=pep8%20E123) closing bracket does not match indentation of opening bracket's line
> [Line 778:13](https://github.com/pandas-dev/pandas/blob/3ff25bdfcc63812afb0288afb12c3720e7b3cdce/pandas/tests/frame/test_constructors.py#L778): [E123](https://duckduckgo.com/?q=pep8%20E123) closing bracket does not match indentation of opening bracket's line





##### Comment last updated on January 03, 2019 at 15:45 Hours UTC
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24581?src=pr&el=h1) Report
> Merging [#24581](https://codecov.io/gh/pandas-dev/pandas/pull/24581?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/4b91140a1068f80c2b6953d8950dbfedde7144c7?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24581/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24581?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24581      +/-   ##
==========================================
+ Coverage   92.36%   92.36%   +<.01%     
==========================================
  Files         166      166              
  Lines       52494    52496       +2     
==========================================
+ Hits        48485    48487       +2     
  Misses       4009     4009
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.79% <100%> (ø)` | :arrow_up: |
| #single | `43.03% <0%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24581?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/24581/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `96.92% <100%> (ø)` | :arrow_up: |
| [pandas/core/internals/construction.py](https://codecov.io/gh/pandas-dev/pandas/pull/24581/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL2NvbnN0cnVjdGlvbi5weQ==) | `96.67% <100%> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24581?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/24581?src=pr&el=footer). Last update [4b91140...b20389d](https://codecov.io/gh/pandas-dev/pandas/pull/24581?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/24581?src=pr&el=h1) Report
> Merging [#24581](https://codecov.io/gh/pandas-dev/pandas/pull/24581?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/4b91140a1068f80c2b6953d8950dbfedde7144c7?src=pr&el=desc) will **increase** coverage by `0.02%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24581/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24581?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24581      +/-   ##
==========================================
+ Coverage   92.36%   92.38%   +0.02%     
==========================================
  Files         166      166              
  Lines       52494    52490       -4     
==========================================
+ Hits        48485    48493       +8     
+ Misses       4009     3997      -12
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.81% <100%> (+0.02%)` | :arrow_up: |
| #single | `43.05% <0%> (+0.01%)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24581?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/24581/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `96.92% <100%> (ø)` | :arrow_up: |
| [pandas/core/internals/construction.py](https://codecov.io/gh/pandas-dev/pandas/pull/24581/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL2NvbnN0cnVjdGlvbi5weQ==) | `96.67% <100%> (ø)` | :arrow_up: |
| [pandas/core/nanops.py](https://codecov.io/gh/pandas-dev/pandas/pull/24581/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvbmFub3BzLnB5) | `94.54% <0%> (-0.37%)` | :arrow_down: |
| [pandas/core/indexes/accessors.py](https://codecov.io/gh/pandas-dev/pandas/pull/24581/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9hY2Nlc3NvcnMucHk=) | `91% <0%> (ø)` | :arrow_up: |
| [pandas/core/indexes/timedeltas.py](https://codecov.io/gh/pandas-dev/pandas/pull/24581/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy90aW1lZGVsdGFzLnB5) | `90.22% <0%> (ø)` | :arrow_up: |
| [pandas/core/arrays/datetimelike.py](https://codecov.io/gh/pandas-dev/pandas/pull/24581/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2RhdGV0aW1lbGlrZS5weQ==) | `97.85% <0%> (ø)` | :arrow_up: |
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/24581/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `96.62% <0%> (ø)` | :arrow_up: |
| [pandas/core/arrays/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/24581/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2RhdGV0aW1lcy5weQ==) | `98.01% <0%> (ø)` | :arrow_up: |
| [pandas/core/arrays/period.py](https://codecov.io/gh/pandas-dev/pandas/pull/24581/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3BlcmlvZC5weQ==) | `98.53% <0%> (+0.01%)` | :arrow_up: |
| [pandas/core/internals/managers.py](https://codecov.io/gh/pandas-dev/pandas/pull/24581/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL21hbmFnZXJzLnB5) | `95.96% <0%> (+0.02%)` | :arrow_up: |
| ... and [2 more](https://codecov.io/gh/pandas-dev/pandas/pull/24581/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24581?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/24581?src=pr&el=footer). Last update [4b91140...ad01a21](https://codecov.io/gh/pandas-dev/pandas/pull/24581?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).

https://dev.azure.com/pandas-dev/pandas/_build/results?buildId=6404 some lint issues as well
lgtm. ping on green.
some lint issues
thanks @karldw 
Thank you!