REGR: unpickling in 1.3.0 DataFrame created in 1.2.x #42345
- [x] closes #42345
- [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
- [x] whatsnew entry

@jbrockmendel ok i think then let's merge this and then backport the full testing of the 1.2.x pickles in 1.3? > yah @meeseeksdev backport 1.3.x Something went wrong ... Please have  a look at my logs.