Might you consider not having sudo as an unconditional dependency?
As you're probably aware, sudo has had some serious security holes, including one that permitted root access to any user on a system where sudo was installed.
Temporary root access for individual commands can also be provided using
su -m root -c 'command args'
I imagine some people may prefer to use sudo despite the risks, so the main thing is simply allowing porttools to be used without having sudo installed if one so chooses.
That could be as simple as dropping the sudo dependency and issuing an error message when it's needed and not installed. Those who want to use sudo with port commands can easily install it separately.