that's not what happens though. what happens is you get conflicting providers where you need to pick if you want python2-vdirsyncer or python3-vdirsyncer, when you asked for "vdirsyncer". (the system is not smart enough to magically figure out whether it should upgrade you to py2 or py3)

if you wrap the obsoletes/provides in %ifpython3, then existing installations of vdirsyncer will migrate to python3. that seems the right thing to me