TST: fix up pandas_datareader downstream tests
closes #18935

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/19490?src=pr&el=h1) Report
> Merging [#19490](https://codecov.io/gh/pandas-dev/pandas/pull/19490?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/3597de0ada3869c8841d05ef4353195a6e124184?src=pr&el=desc) will **increase** coverage by `0.09%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/19490/graphs/tree.svg?token=eZ4WkYLtcO&width=650&src=pr&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/19490?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #19490      +/-   ##
==========================================
+ Coverage   91.67%   91.77%   +0.09%     
==========================================
  Files         148      148              
  Lines       48542    49170     +628     
==========================================
+ Hits        44501    45124     +623     
- Misses       4041     4046       +5
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.13% <ø> (+0.09%)` | :arrow_up: |
| #single | `41.99% <ø> (+0.27%)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/19490?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/pytables.py](https://codecov.io/gh/pandas-dev/pandas/pull/19490/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3B5dGFibGVzLnB5) | `92.61% <0%> (+0.16%)` | :arrow_up: |
| [pandas/io/formats/format.py](https://codecov.io/gh/pandas-dev/pandas/pull/19490/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvZm9ybWF0LnB5) | `96.57% <0%> (+0.32%)` | :arrow_up: |
| [pandas/io/parsers.py](https://codecov.io/gh/pandas-dev/pandas/pull/19490/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3BhcnNlcnMucHk=) | `96.21% <0%> (+0.71%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/19490?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/19490?src=pr&el=footer). Last update [3597de0...203a3b2](https://codecov.io/gh/pandas-dev/pandas/pull/19490?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
