Checks for tz/tzinfo validity in Timestamp.__new__
closes #17690
related #5168

- [x] closes #17690
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17943?src=pr&el=h1) Report
> Merging [#17943](https://codecov.io/gh/pandas-dev/pandas/pull/17943?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/81372093f1fdc0c07e4b45ba0f47b0360fabd405?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/17943/graphs/tree.svg?src=pr&token=eZ4WkYLtcO&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/17943?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17943      +/-   ##
==========================================
- Coverage   91.24%   91.23%   -0.01%     
==========================================
  Files         163      163              
  Lines       50173    50173              
==========================================
- Hits        45778    45774       -4     
- Misses       4395     4399       +4
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.04% <ø> (ø)` | :arrow_up: |
| #single | `40.29% <ø> (-0.06%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17943?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17943?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17943?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.75% <0%> (-0.1%)` | :arrow_down: |
| [pandas/io/msgpack/\_version.py](https://codecov.io/gh/pandas-dev/pandas/pull/17943?src=pr&el=tree#diff-cGFuZGFzL2lvL21zZ3BhY2svX3ZlcnNpb24ucHk=) | `44.65% <0%> (+1.9%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17943?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/17943?src=pr&el=footer). Last update [8137209...98b5b17](https://codecov.io/gh/pandas-dev/pandas/pull/17943?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Just pushed fixes for test errors.  In a nutshell: the more verbose version is also more robust. Travis error in TestClipboard.test_round_trip_valid_encodings looks unrelated. thanks!