TST: Fix xfailing DataFrame arithmetic tests by transposing
- [ ] closes #xxxx
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Hello @jbrockmendel! Thanks for updating the PR.

 - There are no PEP8 issues in the file [`pandas/tests/arithmetic/conftest.py`](https://github.com/jbrockmendel/pandas/blob/2a1ceecd4e63843575d9d7aa9066e5a0283d970c/pandas/tests/arithmetic/conftest.py) !

 - There are no PEP8 issues in the file [`pandas/tests/arithmetic/test_datetime64.py`](https://github.com/jbrockmendel/pandas/blob/2a1ceecd4e63843575d9d7aa9066e5a0283d970c/pandas/tests/arithmetic/test_datetime64.py) !

 - There are no PEP8 issues in the file [`pandas/tests/arithmetic/test_period.py`](https://github.com/jbrockmendel/pandas/blob/2a1ceecd4e63843575d9d7aa9066e5a0283d970c/pandas/tests/arithmetic/test_period.py) !

 - There are no PEP8 issues in the file [`pandas/tests/arithmetic/test_timedelta64.py`](https://github.com/jbrockmendel/pandas/blob/2a1ceecd4e63843575d9d7aa9066e5a0283d970c/pandas/tests/arithmetic/test_timedelta64.py) !

 - There are no PEP8 issues in the file [`pandas/util/testing.py`](https://github.com/jbrockmendel/pandas/blob/2a1ceecd4e63843575d9d7aa9066e5a0283d970c/pandas/util/testing.py) !



##### Comment last updated on November 11, 2018 at 20:09 Hours UTC # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23620?src=pr&el=h1) Report
> Merging [#23620](https://codecov.io/gh/pandas-dev/pandas/pull/23620?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/58a59bd606911f11a4f679df18a00cfc25536c30?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/23620/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/23620?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #23620      +/-   ##
==========================================
+ Coverage   92.23%   92.23%   +<.01%     
==========================================
  Files         161      161              
  Lines       51288    51290       +2     
==========================================
+ Hits        47304    47306       +2     
  Misses       3984     3984
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.62% <100%> (ø)` | :arrow_up: |
| #single | `42.26% <33.33%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/23620?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/23620/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `86.08% <100%> (+0.02%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23620?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/23620?src=pr&el=footer). Last update [58a59bd...2a1ceec](https://codecov.io/gh/pandas-dev/pandas/pull/23620?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 ok ping on green. (also if you have a chance to find the transpose on tz-DTI in a DataFrame issue) and link would be great. ping