BUG: in error message raised when invalid axis parameter
- [x] closes #25555
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

I don't think there is currently an issue for this. will open new and then add whatsnew.
Generally looks good to me. Is this a follow up to another PR? > Generally looks good to me. Is this a follow up to another PR?

@WillAyd : just raised new issue #25555 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25553?src=pr&el=h1) Report
> Merging [#25553](https://codecov.io/gh/pandas-dev/pandas/pull/25553?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/d10bbce349b293e9f753d799cd2ad032d5ec7333?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/25553/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25553?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #25553      +/-   ##
==========================================
+ Coverage   91.75%   91.75%   +<.01%     
==========================================
  Files         173      173              
  Lines       52960    52960              
==========================================
+ Hits        48595    48596       +1     
+ Misses       4365     4364       -1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.33% <100%> (ø)` | :arrow_up: |
| #single | `41.71% <50%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25553?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/25553/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `94.16% <100%> (ø)` | :arrow_up: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/25553/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `87.66% <0%> (+0.09%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25553?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/25553?src=pr&el=footer). Last update [d10bbce...e51d8bc](https://codecov.io/gh/pandas-dev/pandas/pull/25553?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/25553?src=pr&el=h1) Report
> Merging [#25553](https://codecov.io/gh/pandas-dev/pandas/pull/25553?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/3e652ac565e054b763ccbe23006c02704f6cd1b1?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25553/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25553?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #25553      +/-   ##
==========================================
+ Coverage   91.26%   91.26%   +<.01%     
==========================================
  Files         173      173              
  Lines       52966    52966              
==========================================
+ Hits        48337    48338       +1     
+ Misses       4629     4628       -1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.83% <ø> (ø)` | :arrow_up: |
| #single | `41.71% <ø> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25553?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/25553/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `93.65% <ø> (ø)` | :arrow_up: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/25553/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `87.66% <0%> (+0.09%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25553?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/25553?src=pr&el=footer). Last update [3e652ac...b16bc08](https://codecov.io/gh/pandas-dev/pandas/pull/25553?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks @simonjayhawkins 