TST: add downstream deps in 3.6 build
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18333?src=pr&el=h1) Report
> Merging [#18333](https://codecov.io/gh/pandas-dev/pandas/pull/18333?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/d5c490841242e490aa4f510233847861f2ef7144?src=pr&el=desc) will **decrease** coverage by `0.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/18333/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/18333?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #18333      +/-   ##
==========================================
- Coverage   91.38%   91.36%   -0.02%     
==========================================
  Files         164      164              
  Lines       49782    49790       +8     
==========================================
- Hits        45493    45492       -1     
- Misses       4289     4298       +9
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.17% <ø> (ø)` | :arrow_up: |
| #single | `39.49% <ø> (-0.06%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/18333?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/18333?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/18333?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.8% <0%> (-0.1%)` | :arrow_down: |
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/18333?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `95.02% <0%> (+0.01%)` | :arrow_up: |
| [pandas/core/sparse/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/18333?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc3BhcnNlL3Nlcmllcy5weQ==) | `95.33% <0%> (+0.05%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18333?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/18333?src=pr&el=footer). Last update [d5c4908...2ec6aa1](https://codecov.io/gh/pandas-dev/pandas/pull/18333?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18333?src=pr&el=h1) Report
> Merging [#18333](https://codecov.io/gh/pandas-dev/pandas/pull/18333?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/d6049a0efb7c04996bc374f3747bab8fe4c84bac?src=pr&el=desc) will **decrease** coverage by `0.04%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/18333/graphs/tree.svg?height=150&width=650&token=eZ4WkYLtcO&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/18333?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #18333      +/-   ##
==========================================
- Coverage   91.38%   91.34%   -0.05%     
==========================================
  Files         164      164              
  Lines       49790    49790              
==========================================
- Hits        45501    45480      -21     
- Misses       4289     4310      +21
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.14% <ø> (-0.03%)` | :arrow_down: |
| #single | `39.49% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/18333?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/18333/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/18333/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `63.44% <0%> (-1.82%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/18333/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.8% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18333?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/18333?src=pr&el=footer). Last update [d6049a0...1627097](https://codecov.io/gh/pandas-dev/pandas/pull/18333?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 In which travis build are those tested? these are now on the main 3.6 build via conda

they are also on the 3,6_BUILD_TEST via pip
but this was not failing when a test failed (need the -e on bash)
