DOC: Link to Python 3 versions of official Python docs
- [X] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`

Went through and made sure that all links to the official Python docs start with `https://docs.python.org/3/` to ensure that the links go to the most recent stable version of Python 3.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18962?src=pr&el=h1) Report
> Merging [#18962](https://codecov.io/gh/pandas-dev/pandas/pull/18962?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/e56794984f17d1651d74e6dbcdbf77fbec53d45f?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/18962/graphs/tree.svg?token=eZ4WkYLtcO&width=650&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/18962?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #18962   +/-   ##
=======================================
  Coverage   91.59%   91.59%           
=======================================
  Files         150      150           
  Lines       48924    48924           
=======================================
  Hits        44813    44813           
  Misses       4111     4111
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.95% <ø> (ø)` | :arrow_up: |
| #single | `41.16% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/18962?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/computation/eval.py](https://codecov.io/gh/pandas-dev/pandas/pull/18962/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tcHV0YXRpb24vZXZhbC5weQ==) | `97.11% <ø> (ø)` | :arrow_up: |
| [pandas/core/indexes/datetimelike.py](https://codecov.io/gh/pandas-dev/pandas/pull/18962/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZWxpa2UucHk=) | `97.19% <ø> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18962?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/18962?src=pr&el=footer). Last update [e567949...8c18942](https://codecov.io/gh/pandas-dev/pandas/pull/18962?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks!