Drop support for python 2

[jeffwidman]

It's probably time we dropped support for python 2:

flask-debugtoolbar/setup.cfg

Line 33 in e3c8ab0

python_requires = >=2.7

Given that Flask requires 3.7, I'd be fine with jumping straight to that... anyone who is on an older version of python can continue using an older version of Flask.

There's no immediate pressing need to jump to the latest python, but it makes future contributors lives easier because they don't have to worry about such a wide swathe of backwards compatibility.

First though we should push a final 2.x compatible release, that's tracked in #192... only once that's done should we do this.

[jeffwidman]

A new release is out, that will be the final 2.x compatible release: https://pypi.org/project/Flask-DebugToolbar/0.14.0/

Dropping 2.7 is tracked as part of:

• Drop support for Flask < 2.2.0 (and implicitly Python < 3.7) #222

So closing this as a duplicate.