System: debian stretch with xpra/winswitch repository.
I've updated my system today and got xpra 2.1-r16032M-1. Every try to run xpra (even xpra --version) results in
Error: xpra for python 2.7 is not installed
I switched back to 2.0.2-r15657-1, and everything works fine.
Thanks for pointing that out, some beta packages wrongly landed in the stable repo (fortunately this only affected stretch). The actual bug in the beta package has been fixed in r15943.
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/1554