BUG: Fix for GH #14848 for groupby().describe() with tuples as the Index
 - [x] closes #14848 
 - [x ] tests added / passed
 - [x ] passes ``git diff upstream/master | flake8 --diff``
 - [x ] whatsnew entry

This isn't the most elegant fix for the bug, but all the tests pass.  There is probably a bigger issue to deal with here, which is to support tuples as an `Index` (as opposed to a `MultiIndex`) throughout, but at least this fix clears the bug.
this is not going to be acceptable as a fix. way too hacky and special cased. I don't know where the actual issue is, but this needs more investigation. @jreback I had a feeling you'd say that.  I will see if there is a better fix. @Dr-Irv yeah, sorry about that....just want to find the root cause here. thanks! ## [Current coverage](https://codecov.io/gh/pandas-dev/pandas/pull/15110?src=pr) is 84.76% (diff: 100%)
> Merging [#15110](https://codecov.io/gh/pandas-dev/pandas/pull/15110?src=pr) into [master](https://codecov.io/gh/pandas-dev/pandas/branch/master?src=pr) will increase coverage by **<.01%**

```diff
@@             master     #15110   diff @@
==========================================
  Files           145        145          
  Lines         51232      51274    +42   
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
+ Hits          43420      43460    +40   
- Misses         7812       7814     +2   
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last update [0fe491d...c18c6cb](https://codecov.io/gh/pandas-dev/pandas/compare/0fe491db358204544814aa2371fed4ea947532ab...c18c6cbc01e8b2a0fc564efdebc2a203e2201f32?src=pr) @jreback Found the root cause, so this should be good to go. you can prob fix it for this issue is fine  ok, lgtm. ping on green. thanks @Dr-Irv !