webargs 6.0.0 is the result of an important refactor.

The new "one location per schema" approach unlocks the use of schema-level features such as pre/post processors or dealing with unknown fields.

We also dropped Python 2 and moved from Falcon 1 to Falcon 2.

This, plus internal changes that should ease maintenance in the future.

See the changelog for details, which includes an exhaustive listing of breaking changes and instructions on how to update your code.