Bug#1007212: python3-defcon: multiple circular dependencies

[James GK]

I think ufolib2 is an optional dependency for fonttools. It's used in
a standalone tool that's not technically part of the fonttools
library, and if it's not installed at runtime, defcon will be used
instead:
https://github.com/fonttools/fonttools/blob/main/Lib/fontTools/cu2qu/cli.py#L13