separate DatetimeIndex timezone tests
There is probably some overlap with other tests.indexes.datetimes modules.  We'll get those in the next pass.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/19545?src=pr&el=h1) Report
> Merging [#19545](https://codecov.io/gh/pandas-dev/pandas/pull/19545?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/93c86aa13e1b7816c762b4ff372aef80a7830af8?src=pr&el=desc) will **increase** coverage by `0.02%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/19545/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/19545?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #19545      +/-   ##
==========================================
+ Coverage    91.6%   91.63%   +0.02%     
==========================================
  Files         150      150              
  Lines       48750    48750              
==========================================
+ Hits        44657    44670      +13     
+ Misses       4093     4080      -13
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90% <ø> (+0.02%)` | :arrow_up: |
| #single | `41.75% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/19545?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/parsers.py](https://codecov.io/gh/pandas-dev/pandas/pull/19545/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3BhcnNlcnMucHk=) | `95.56% <0%> (+0.06%)` | :arrow_up: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/19545/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `66.95% <0%> (+1.73%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/19545?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/19545?src=pr&el=footer). Last update [93c86aa...aa57279](https://codecov.io/gh/pandas-dev/pandas/pull/19545?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks. if you can add the above items to the master TODO list would be great. I know minor, but don't want to forget about them; at the same time no reason to hold up merging this. Will do.  I appreciate the leeway.