TST: set multi_statement flag for pymysql tests
Trying something out for #19462

closes #19462
Hello @jorisvandenbossche! Thanks for updating the PR.



Cheers ! There are no PEP8 issues in this Pull Request. :beers: 

##### Comment last updated on February 09, 2018 at 15:10 Hours UTC # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/19619?src=pr&el=h1) Report
> Merging [#19619](https://codecov.io/gh/pandas-dev/pandas/pull/19619?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/7dcc86443fd9b1aa94b6f7e4e33b6fbd0210b8db?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/19619/graphs/tree.svg?token=eZ4WkYLtcO&src=pr&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/19619?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #19619   +/-   ##
=======================================
  Coverage   91.62%   91.62%           
=======================================
  Files         150      150           
  Lines       48795    48795           
=======================================
  Hits        44706    44706           
  Misses       4089     4089
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.99% <ø> (ø)` | :arrow_up: |
| #single | `41.72% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/19619?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/19619?src=pr&el=footer). Last update [7dcc864...9d6cb64](https://codecov.io/gh/pandas-dev/pandas/pull/19619?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Seems to be passing now, so merging.