Fix for Python 3.13
This fixes the following error on launch:
Traceback (most recent call last):
File "/usr/bin/gnome-keysign", line 8, in <module>
sys.exit(main())
~~~~^^
File "/usr/lib/python3.13/site-packages/keysign/__init__.py", line 22, in main
from . import app
File "/usr/lib/python3.13/site-packages/keysign/app.py", line 50, in <module>
from .avahioffer import AvahiHTTPOffer
File "/usr/lib/python3.13/site-packages/keysign/avahioffer.py", line 39, in <module>
from .gpgmeh import get_usable_keys, get_public_key_data
File "/usr/lib/python3.13/site-packages/keysign/gpgmeh.py", line 34, in <module>
from .gpgkey import Key, UID
UnicodeEncodeError: 'utf-8' codec can't encode character '\udcf6' in position 118: surrogates not allowed