TST: categorical reindex with added categories
- [x] closes #42424 
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [ ] whatsnew entry

The bug is specifically in the Interval index. The error arises in the example code from the issue while reindexing the categorical index with another categorical index(with new categories). 

The test (test_cut_with_nonexact_categorical_indices)  from PR [42425](https://github.com/pandas-dev/pandas/pull/42425) implicitly works in a similar way.
 

Thanks for the PR @Sheogorath27 - mind taking a look at why CI is failing?  I checked tests are passing locally. And I did not find any conflicts with the failed test. Could you add a unit test with the example in the original issue as well (for an additional smoke test)? Test from PR [42425](https://github.com/pandas-dev/pandas/pull/42425) is the same as the example in the issue. Should I duplicate it? > Test from PR [42425](https://github.com/pandas-dev/pandas/pull/42425) is the same as the example in the issue. Should I duplicate it?

That PR was never merged. What are you suggesting we duplicate?  > > Test from PR [42425](https://github.com/pandas-dev/pandas/pull/42425) is the same as the example in the issue. Should I duplicate it?
> 
> That PR was never merged. What are you suggesting we duplicate?

Sorry, I assumed PR was merged. I will add a new unit test. > Could you add a unit test with the example in the original issue as well (for an additional smoke test)?

I have added a new test based on the example from the issue. Thanks @Sheogorath27 