TST: Skip test_database_uri_string if pg8000 importable
 - [x] closes #16527
 - [x] tests added / passed
 - [x] passes ``git diff upstream/master --name-only -- '*.py' | flake8 --diff``
 - [ ] whatsnew entry
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16528?src=pr&el=h1) Report
> Merging [#16528](https://codecov.io/gh/pandas-dev/pandas/pull/16528?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/e60dc4cff2c6e8a2283fbb906faeb8cb01df37ff?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16528/graphs/tree.svg?src=pr&width=650&token=eZ4WkYLtcO&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/16528?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16528      +/-   ##
==========================================
- Coverage   90.79%   90.79%   -0.01%     
==========================================
  Files         161      161              
  Lines       51063    51063              
==========================================
- Hits        46365    46364       -1     
- Misses       4698     4699       +1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.63% <ø> (-0.01%)` | :arrow_down: |
| #single | `40.15% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16528?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/16528?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `95.23% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16528?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/16528?src=pr&el=footer). Last update [e60dc4c...e22541b](https://codecov.io/gh/pandas-dev/pandas/pull/16528?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/16528?src=pr&el=h1) Report
> Merging [#16528](https://codecov.io/gh/pandas-dev/pandas/pull/16528?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/e60dc4cff2c6e8a2283fbb906faeb8cb01df37ff?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/16528/graphs/tree.svg?token=eZ4WkYLtcO&src=pr&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/16528?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #16528   +/-   ##
=======================================
  Coverage   90.79%   90.79%           
=======================================
  Files         161      161           
  Lines       51063    51063           
=======================================
  Hits        46365    46365           
  Misses       4698     4698
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.63% <ø> (ø)` | :arrow_up: |
| #single | `40.15% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16528?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/16528?src=pr&el=footer). Last update [e60dc4c...e22541b](https://codecov.io/gh/pandas-dev/pandas/pull/16528?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @jorisvandenbossche ok? This looks good, thanks. Yes, perfect! Thanks @neirbowj 