[CLN] bit refactoring for io.parsers
State: closed

just some small cosmetics. Let me know if small cleanup PRs like this are welcome. :)

Labels:
name: Refactor
description: Internal refactoring of code
name: IO Data
description: IO issues that don't fit into a more specific label

Comments:
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25201?src=pr&el=h1) Report
> Merging [#25201](https://codecov.io/gh/pandas-dev/pandas/pull/25201?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/638ddebaa7da1e569836a5b89593b120dbbf491c?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25201/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25201?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #25201      +/-   ##
==========================================
- Coverage   92.35%   92.34%   -0.01%     
==========================================
  Files         166      166              
  Lines       52314    52302      -12     
==========================================
- Hits        48312    48299      -13     
- Misses       4002     4003       +1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.78% <100%> (-0.01%)` | :arrow_down: |
| #single | `42.84% <50%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25201?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/parsers.py](https://codecov.io/gh/pandas-dev/pandas/pull/25201/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3BhcnNlcnMucHk=) | `95.31% <100%> (-0.04%)` | :arrow_down: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/25201/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `87.95% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25201?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/25201?src=pr&el=footer). Last update [638ddeb...62cb924](https://codecov.io/gh/pandas-dev/pandas/pull/25201?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/25201?src=pr&el=h1) Report
> Merging [#25201](https://codecov.io/gh/pandas-dev/pandas/pull/25201?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/638ddebaa7da1e569836a5b89593b120dbbf491c?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25201/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25201?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #25201      +/-   ##
==========================================
- Coverage   92.35%   92.34%   -0.01%     
==========================================
  Files         166      166              
  Lines       52314    52302      -12     
==========================================
- Hits        48312    48299      -13     
- Misses       4002     4003       +1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.78% <100%> (-0.01%)` | :arrow_down: |
| #single | `42.84% <50%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25201?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/parsers.py](https://codecov.io/gh/pandas-dev/pandas/pull/25201/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3BhcnNlcnMucHk=) | `95.31% <100%> (-0.04%)` | :arrow_down: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/25201/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `87.95% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25201?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/25201?src=pr&el=footer). Last update [638ddeb...62cb924](https://codecov.io/gh/pandas-dev/pandas/pull/25201?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).

not really sure what this PR is attempting to solve.