Log Message:
py-klein: updated to 21.8.0 (finish parial update)

21.8.0 - 2021-08-08

Python 2 is no longer supported by Klein.
Python 3.5 is no longer supported by Klein.
Python 3.9 is now supported by Klein.
Fixed a compatibility issue with Twisted versions greater than 20.3.0 in Klein's \ 
test suite.
Fixed a compatibility issue with Werkzeug versions greater than 2.0 in Klein's \ 
test suite.
Klein has incomplete, but growing type hints, but py.typed is not installed, as \ 
they might not work well for most clients yet.
Plating now sets the Content-Type header to application/json instead of \ 
text/json; charset=utf8.