When upgrading xpra:
Setting up xpra (3.1.5+dfsg1-0.2+b2) ...
/usr/lib/python3/dist-packages/xpra/scripts/main.py:2758: SyntaxWarning: invalid escape sequence '\.'
alphanum = lambda key: [convert(c) for c in re.split('([-+]?[0-9]*\.?[0-9]*)', key)]