Continue Collecting Arithmetic Tests
A small amount of cleanup/parametrization, but mostly moving tests ~unchanged.

A few tests in tests.frame.test_operators are moved to tests.frame.test_arithmetic.

In a bunch of cases I'm trying to not move things that will cause merge conflicts with #22163; will get those in an upcoming pass.
Hello @jbrockmendel! Thanks for updating the PR.







 - In the file [`pandas/tests/frame/test_arithmetic.py`](https://github.com/pandas-dev/pandas/blob/f18ba2e9652d2a2cca6023f5bcd91a18ee92224d/pandas/tests/frame/test_arithmetic.py), following are the PEP8 issues :

> [Line 170:13](https://github.com/pandas-dev/pandas/blob/f18ba2e9652d2a2cca6023f5bcd91a18ee92224d/pandas/tests/frame/test_arithmetic.py#L170): [E722](https://duckduckgo.com/?q=pep8%20E722) do not use bare except'











##### Comment last updated on August 09, 2018 at 22:34 Hours UTC looks fine. ping on green. (go ahead and merge) # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22267?src=pr&el=h1) Report
> Merging [#22267](https://codecov.io/gh/pandas-dev/pandas/pull/22267?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/475e391eaa0c85c4615ad6da5f81dee9b890635b?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/22267/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/22267?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #22267   +/-   ##
=======================================
  Coverage   92.08%   92.08%           
=======================================
  Files         169      169           
  Lines       50704    50704           
=======================================
  Hits        46691    46691           
  Misses       4013     4013
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.49% <ø> (ø)` | :arrow_up: |
| #single | `42.33% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22267?src=pr&el=continue).
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> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22267?src=pr&el=footer). Last update [475e391...f18ba2e](https://codecov.io/gh/pandas-dev/pandas/pull/22267?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks