I wrote too many words.  In short:

time.sleep()'s behavior should remain as it is today given how it is documented to behave.  If you disagree, consider adding an optional interruptable=False parameter so that both behavior options exist.

ALL IO calls and wait* should handle EINTR transparently for the user and never expose it to the Python application.

select(), poll() and equivalents.  If you want to transparently handle EINTR on these, just make sure you deal with the timeouts properly.  While I suspect a few people wanted to see the signal interruption on those I agree: very uncommon and undesirable for most.

If people need a specific signal interruption they should define a signal handler that raises.