Avoid requiring PyQt5 when just building cli

[jonasnick]

If I understand correctly, you can't build liquid-swap-cli without requiring PyQt5. In nix-bitcoin we're only interested in the cli and try to avoid as many unnecessary dependencies as possible. So it would be nice if in the future we could skip PyQt5 altogether.

[LeoComandini]

05bc359 should have fixed it. Now pip install .[CLI] does not install PyQt5. Upgrading to 0.0.2 should fix the problem.

[jonasnick]

perfect, thanks!