MAINT: asv with py3 on windows
 Since benchmarking on python 3, no longer want to install `libpython`

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16139?src=pr&el=h1) Report
> Merging [#16139](https://codecov.io/gh/pandas-dev/pandas/pull/16139?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/d50b1620ca57a37c0c005ae946b9fc45020e2155?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/16139/graphs/tree.svg?src=pr&token=eZ4WkYLtcO&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/16139?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #16139   +/-   ##
=======================================
  Coverage   90.84%   90.84%           
=======================================
  Files         159      159           
  Lines       50779    50779           
=======================================
  Hits        46128    46128           
  Misses       4651     4651
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.62% <ø> (ø)` | :arrow_up: |
| #single | `40.33% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16139?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/16139?src=pr&el=footer). Last update [d50b162...c8b3853](https://codecov.io/gh/pandas-dev/pandas/pull/16139?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/16139?src=pr&el=h1) Report
> Merging [#16139](https://codecov.io/gh/pandas-dev/pandas/pull/16139?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/d50b1620ca57a37c0c005ae946b9fc45020e2155?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/16139/graphs/tree.svg?token=eZ4WkYLtcO&width=650&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/16139?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #16139   +/-   ##
=======================================
  Coverage   90.84%   90.84%           
=======================================
  Files         159      159           
  Lines       50779    50779           
=======================================
  Hits        46128    46128           
  Misses       4651     4651
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.62% <ø> (ø)` | :arrow_up: |
| #single | `40.33% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16139?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/16139?src=pr&el=footer). Last update [d50b162...c8b3853](https://codecov.io/gh/pandas-dev/pandas/pull/16139?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/16139?src=pr&el=h1) Report
> Merging [#16139](https://codecov.io/gh/pandas-dev/pandas/pull/16139?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/d50b1620ca57a37c0c005ae946b9fc45020e2155?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/16139/graphs/tree.svg?token=eZ4WkYLtcO&src=pr&height=150&width=650)](https://codecov.io/gh/pandas-dev/pandas/pull/16139?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #16139   +/-   ##
=======================================
  Coverage   90.84%   90.84%           
=======================================
  Files         159      159           
  Lines       50779    50779           
=======================================
  Hits        46128    46128           
  Misses       4651     4651
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.62% <ø> (ø)` | :arrow_up: |
| #single | `40.33% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16139?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/16139?src=pr&el=footer). Last update [d50b162...42f47bc](https://codecov.io/gh/pandas-dev/pandas/pull/16139?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Can you keep those entries but specify it is only for python 3? 
Then for people benchmarking on python 2, it keeps working @jorisvandenbossche - asv actually still works on python 2 with this change, as long as the right version of MSVC is installed (https://www.microsoft.com/en-us/download/details.aspx?id=44266).

This would be the same compiler our release binaries / tests are built with, and easy enough to install now (wasn't always), so I think we should prefer it over the `mingw` toolchain. OK, I currently don't use python 2 on windows anymore, so won't push too hard. I just know that being able to just conda install the correct compilers was very handy at that time :-) But if that has improved, then certainly OK!

Our contributing docs still mention `libpython`: http://pandas-docs.github.io/pandas-docs-travis/contributing.html#creating-a-windows-development-environment Yeah, that's fair, I think MSVC would be the 'recommended' way now, but `libpython` is still valid for 2.x.  I added a comment that hopefully is a decent middle ground? thanks!