Remove plugin system

[heuer]

Apart from qrcode-artistic, there are no known plugins for Segno. In addition, there are always problems with users assuming that the functionality of the plugin belongs to Segno.

Plugins should no longer be supported.

[StephanosPSteer]

Oh I see I have been trying to get the pacman plugin working. Any chance you can add those bits of functionality?

[heuer]

Oh I see I have been trying to get the pacman plugin working. Any chance you can add those bits of functionality?

The plugin-system is still there but Segno's API changed a bit since I published the pacman code. The code is not maintained anymore, but I updated it to work with the current Segno release, see https://github.com/heuer/segno-quark/blob/master/segno_quark.py

Quick test:

Feel free to fork the above mentioned repository, I don't have any interest in the code anymore.

[heuer]

More reasons why the plugin system should be removed:
lincolnloop/python-qrcode#378
#141

It was a smart or funny idea back then but it took not off.