Move core.config to _config.config
and update imports.  Move `tests.test_config` to `tests.config.test_config`.

Following this there will be one more follow-up that will 1) address the TODO in `tests.config.test_localization`, 2) fully disentangle `tslibs` from its dependency on `core`.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25793?src=pr&el=h1) Report
> Merging [#25793](https://codecov.io/gh/pandas-dev/pandas/pull/25793?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/fb11912e5ea512ccd9fe0aa058920fd8d83f506f?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `92.85%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25793/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25793?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #25793      +/-   ##
==========================================
+ Coverage   91.26%   91.26%   +<.01%     
==========================================
  Files         173      174       +1     
  Lines       52982    52984       +2     
==========================================
+ Hits        48355    48357       +2     
  Misses       4627     4627
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.83% <92.85%> (ø)` | :arrow_up: |
| #single | `41.76% <82.14%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25793?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/\_config/config.py](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree#diff-cGFuZGFzL19jb25maWcvY29uZmlnLnB5) | `86.82% <ø> (ø)` | |
| [pandas/core/api.py](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXBpLnB5) | `100% <ø> (ø)` | :arrow_up: |
| [pandas/core/dtypes/dtypes.py](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL2R0eXBlcy5weQ==) | `96.1% <0%> (ø)` | :arrow_up: |
| [pandas/io/formats/console.py](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvY29uc29sZS5weQ==) | `86.27% <0%> (ø)` | :arrow_up: |
| [pandas/core/computation/expressions.py](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tcHV0YXRpb24vZXhwcmVzc2lvbnMucHk=) | `93.27% <100%> (ø)` | :arrow_up: |
| [pandas/core/indexes/multi.py](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9tdWx0aS5weQ==) | `95.62% <100%> (ø)` | :arrow_up: |
| [pandas/io/formats/format.py](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvZm9ybWF0LnB5) | `97.99% <100%> (ø)` | :arrow_up: |
| [pandas/core/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYmFzZS5weQ==) | `97.76% <100%> (ø)` | :arrow_up: |
| [pandas/plotting/\_core.py](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb3JlLnB5) | `83.65% <100%> (ø)` | :arrow_up: |
| [pandas/io/formats/html.py](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvaHRtbC5weQ==) | `99.35% <100%> (ø)` | :arrow_up: |
| ... and [17 more](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25793?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/25793?src=pr&el=footer). Last update [fb11912...0e28708](https://codecov.io/gh/pandas-dev/pandas/pull/25793?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/25793?src=pr&el=h1) Report
> Merging [#25793](https://codecov.io/gh/pandas-dev/pandas/pull/25793?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/0f5a7e3a6edace63fcb342a1a0187856aee24b93?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `92.85%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25793/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25793?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #25793      +/-   ##
==========================================
+ Coverage   91.47%   91.47%   +<.01%     
==========================================
  Files         172      173       +1     
  Lines       52870    52872       +2     
==========================================
+ Hits        48362    48364       +2     
  Misses       4508     4508
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.03% <92.85%> (ø)` | :arrow_up: |
| #single | `41.82% <82.14%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25793?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/\_config/config.py](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree#diff-cGFuZGFzL19jb25maWcvY29uZmlnLnB5) | `86.82% <ø> (ø)` | |
| [pandas/core/api.py](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXBpLnB5) | `100% <ø> (ø)` | :arrow_up: |
| [pandas/core/dtypes/dtypes.py](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL2R0eXBlcy5weQ==) | `96.1% <0%> (ø)` | :arrow_up: |
| [pandas/io/formats/console.py](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvY29uc29sZS5weQ==) | `86.27% <0%> (ø)` | :arrow_up: |
| [pandas/core/computation/expressions.py](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tcHV0YXRpb24vZXhwcmVzc2lvbnMucHk=) | `93.27% <100%> (ø)` | :arrow_up: |
| [pandas/core/indexes/multi.py](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9tdWx0aS5weQ==) | `95.62% <100%> (ø)` | :arrow_up: |
| [pandas/io/formats/format.py](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvZm9ybWF0LnB5) | `97.99% <100%> (ø)` | :arrow_up: |
| [pandas/core/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYmFzZS5weQ==) | `97.76% <100%> (ø)` | :arrow_up: |
| [pandas/plotting/\_core.py](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb3JlLnB5) | `83.65% <100%> (ø)` | :arrow_up: |
| [pandas/io/formats/html.py](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvaHRtbC5weQ==) | `99.35% <100%> (ø)` | :arrow_up: |
| ... and [17 more](https://codecov.io/gh/pandas-dev/pandas/pull/25793/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25793?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/25793?src=pr&el=footer). Last update [0f5a7e3...8655437](https://codecov.io/gh/pandas-dev/pandas/pull/25793?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 ```
ImportError while importing test module 'D:\a\1\s\pandas\tests\sparse\test_format.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
pandas\tests\sparse\test_format.py:9: in <module>
    from pandas.core.config import option_context
E   ModuleNotFoundError: No module named 'pandas.core.config'
============================== warnings summary ================
``` Fixed can you rebase rebased+green Hello @jbrockmendel! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:















































































There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2019-03-24 15:48:29 UTC sorry, can you rebase again :< looks good otherwise. thanks @jbrockmendel 