Dulwich 0.20 will drop support for Python 2

[Jelmer Vernooij]

The upcoming Dulwich 0.20 release series will drop support for any Python
versions older than 3.5.

If you do still need support for Python 2, please update your dependencies to
require a version of Dulwich before 0.20, e.g. by adding something like this to
your dependencies:

dulwich<0.20;python_version<"3.0"

There may be more minor releases in the 0.19 series (which will continue to
support Python 2 and Python 3), for bug fixes only.

Cheers,

Jelmer