REF: strictness and checks for Timedelta _simple_new
Broken off from #23426.

- [x] closes #9462
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Hello @jbrockmendel! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/core/arrays/timedeltas.py`](https://github.com/jbrockmendel/pandas/blob/5edf59a2aa6cce0b450b2830eb360b0c49152931/pandas/core/arrays/timedeltas.py) !

 - There are no PEP8 issues in the file [`pandas/core/indexes/base.py`](https://github.com/jbrockmendel/pandas/blob/5edf59a2aa6cce0b450b2830eb360b0c49152931/pandas/core/indexes/base.py) !

 - There are no PEP8 issues in the file [`pandas/core/indexes/timedeltas.py`](https://github.com/jbrockmendel/pandas/blob/5edf59a2aa6cce0b450b2830eb360b0c49152931/pandas/core/indexes/timedeltas.py) !

 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23433?src=pr&el=h1) Report
> Merging [#23433](https://codecov.io/gh/pandas-dev/pandas/pull/23433?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/4f717551b8e49ecd978bb4f5a985d6f6a96d86e9?src=pr&el=desc) will **decrease** coverage by `0.01%`.
> The diff coverage is `93.33%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/23433/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/23433?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #23433      +/-   ##
==========================================
- Coverage   92.22%   92.21%   -0.02%     
==========================================
  Files         161      161              
  Lines       51187    51188       +1     
==========================================
- Hits        47209    47202       -7     
- Misses       3978     3986       +8
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.64% <93.33%> (+0.03%)` | :arrow_up: |
| #single | `42.24% <73.33%> (-0.03%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/23433?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/indexes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/23433/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9iYXNlLnB5) | `96.51% <100%> (+0.05%)` | :arrow_up: |
| [pandas/core/arrays/timedeltas.py](https://codecov.io/gh/pandas-dev/pandas/pull/23433/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3RpbWVkZWx0YXMucHk=) | `94.27% <90%> (-0.03%)` | :arrow_down: |
| [pandas/core/indexes/timedeltas.py](https://codecov.io/gh/pandas-dev/pandas/pull/23433/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy90aW1lZGVsdGFzLnB5) | `90.74% <94.11%> (+0.12%)` | :arrow_up: |
| [pandas/io/feather\_format.py](https://codecov.io/gh/pandas-dev/pandas/pull/23433/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2ZlYXRoZXJfZm9ybWF0LnB5) | `77.14% <0%> (-12.61%)` | :arrow_down: |
| [pandas/core/arrays/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/23433/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2RhdGV0aW1lcy5weQ==) | `97.9% <0%> (-0.95%)` | :arrow_down: |
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/23433/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `95.82% <0%> (-0.6%)` | :arrow_down: |
| [pandas/core/indexes/multi.py](https://codecov.io/gh/pandas-dev/pandas/pull/23433/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9tdWx0aS5weQ==) | `95.46% <0%> (-0.01%)` | :arrow_down: |
| [pandas/core/resample.py](https://codecov.io/gh/pandas-dev/pandas/pull/23433/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzYW1wbGUucHk=) | `96.98% <0%> (-0.01%)` | :arrow_down: |
| [pandas/core/reshape/pivot.py](https://codecov.io/gh/pandas-dev/pandas/pull/23433/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9waXZvdC5weQ==) | `96.55% <0%> (ø)` | :arrow_up: |
| [pandas/core/computation/align.py](https://codecov.io/gh/pandas-dev/pandas/pull/23433/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tcHV0YXRpb24vYWxpZ24ucHk=) | `97.89% <0%> (ø)` | :arrow_up: |
| ... and [22 more](https://codecov.io/gh/pandas-dev/pandas/pull/23433/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23433?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/23433?src=pr&el=footer). Last update [4f71755...e7dd05e](https://codecov.io/gh/pandas-dev/pandas/pull/23433?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Travis failure is for (new?) linting in scripts/docs Gentle ping,  I’m hoping to make a big push on datetime/timedelta array this weekend, getting the constructors locked down is the first step. ok merging.