CLN: Remove vestigial references to PY2 in tests
xref #25725
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25865?src=pr&el=h1) Report
> Merging [#25865](https://codecov.io/gh/pandas-dev/pandas/pull/25865?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/9821b77de692716d7c2b62db1a68cac9ffc456c3?src=pr&el=desc) will **decrease** coverage by `49.65%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25865/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25865?src=pr&el=tree)

```diff
@@             Coverage Diff             @@
##           master   #25865       +/-   ##
===========================================
- Coverage   91.47%   41.82%   -49.66%     
===========================================
  Files         173      173               
  Lines       52872    52872               
===========================================
- Hits        48366    22112    -26254     
- Misses       4506    30760    +26254
```

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

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25865?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/formats/latex.py](https://codecov.io/gh/pandas-dev/pandas/pull/25865/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvbGF0ZXgucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/io/sas/sas\_constants.py](https://codecov.io/gh/pandas-dev/pandas/pull/25865/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXNfY29uc3RhbnRzLnB5) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/tseries/plotting.py](https://codecov.io/gh/pandas-dev/pandas/pull/25865/diff?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvcGxvdHRpbmcucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/tseries/converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/25865/diff?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvY29udmVydGVyLnB5) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/io/formats/html.py](https://codecov.io/gh/pandas-dev/pandas/pull/25865/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvaHRtbC5weQ==) | `0% <0%> (-99.36%)` | :arrow_down: |
| [pandas/core/groupby/categorical.py](https://codecov.io/gh/pandas-dev/pandas/pull/25865/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ3JvdXBieS9jYXRlZ29yaWNhbC5weQ==) | `0% <0%> (-95.46%)` | :arrow_down: |
| [pandas/io/sas/sas7bdat.py](https://codecov.io/gh/pandas-dev/pandas/pull/25865/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXM3YmRhdC5weQ==) | `0% <0%> (-91.17%)` | :arrow_down: |
| [pandas/io/sas/sas\_xport.py](https://codecov.io/gh/pandas-dev/pandas/pull/25865/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXNfeHBvcnQucHk=) | `0% <0%> (-90.15%)` | :arrow_down: |
| [pandas/core/tools/numeric.py](https://codecov.io/gh/pandas-dev/pandas/pull/25865/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvdG9vbHMvbnVtZXJpYy5weQ==) | `10.44% <0%> (-89.56%)` | :arrow_down: |
| [pandas/io/json/normalize.py](https://codecov.io/gh/pandas-dev/pandas/pull/25865/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2pzb24vbm9ybWFsaXplLnB5) | `8.16% <0%> (-88.78%)` | :arrow_down: |
| ... and [129 more](https://codecov.io/gh/pandas-dev/pandas/pull/25865/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25865?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/25865?src=pr&el=footer). Last update [9821b77...7317a79](https://codecov.io/gh/pandas-dev/pandas/pull/25865?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/25865?src=pr&el=h1) Report
> Merging [#25865](https://codecov.io/gh/pandas-dev/pandas/pull/25865?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/9821b77de692716d7c2b62db1a68cac9ffc456c3?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/25865/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25865?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #25865   +/-   ##
=======================================
  Coverage   91.47%   91.47%           
=======================================
  Files         173      173           
  Lines       52872    52872           
=======================================
  Hits        48366    48366           
  Misses       4506     4506
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.04% <ø> (ø)` | :arrow_up: |
| #single | `41.82% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25865?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/25865?src=pr&el=footer). Last update [9821b77...649f6ce](https://codecov.io/gh/pandas-dev/pandas/pull/25865?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks @gfyoung 