DOC: fixed dynamic import mechanics of make.py
- [X] closes #20001 
- [ ] tests added / passed
- [X] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry
Looks good to me. I suppose this works for you?

cc @datapythonista  Yes, well spotted. Didn't realize the imported pandas wasn't being affected by the path. # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/20005?src=pr&el=h1) Report
> :exclamation: No coverage uploaded for pull request base (`master@aedbd94`). [Click here to learn what that means](https://docs.codecov.io/docs/error-reference#section-missing-base-commit).
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/20005/graphs/tree.svg?src=pr&token=eZ4WkYLtcO&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/20005?src=pr&el=tree)

```diff
@@            Coverage Diff            @@
##             master   #20005   +/-   ##
=========================================
  Coverage          ?   91.68%           
=========================================
  Files             ?      150           
  Lines             ?    49065           
  Branches          ?        0           
=========================================
  Hits              ?    44986           
  Misses            ?     4079           
  Partials          ?        0
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.06% <ø> (?)` | |
| #single | `41.88% <ø> (?)` | |


------

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> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/20005?src=pr&el=footer). Last update [aedbd94...84b8bcb](https://codecov.io/gh/pandas-dev/pandas/pull/20005?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Checked Travis failures and none look related to this change Thanks!