[Twisted-Python] How to configure setup.py for a twistd TAP app

[Chris Miles]

I want to deploy my Twisted app as a Twisted Application Plugin for  
twistd as per
http://twistedmatrix.com/projects/core/documentation/howto/tap.html

I want to distribute my app as a tarball, so the user would untar it  
and run "python setup.py install".  Then they would run "twistd myapp"  
to start it.

How do I configure setup.py so that twisted/plugins/myapp.py is created?

Where do I create the twisted/plugins directory?

(I see how this works if I run twistd from the directory containing  
twisted/plugins, or if I set PYTHONPATH, but I don't expect my users  
to have to do this).

Cheers,
Chris