require Python 3.3+ on startup
minor change
stat first before callbacks

so that when the callbacks run, the paths are more likely to exist
test updated
bump version
avoid to create symlink loops
typo in same_existent_file
move remove_old_packages to elsewhere
run next command when this one fails
multiple actions to same package, let's do latter

That is, existing + add + remove = removed
Merge remote-tracking branch 'github/master'