python-apt create_pin question

[Antonio Russo <aerusso@aerusso.net>]

Hello!

I'm trying to use apt_pkg to get a "best candidate" for a package, but with
slightly different constraints than I have set up in /etc/apt/preferences.d.

I am trying to use Policy.create_pin to do so, but cannot seem to get it working:

import apt_pkg

apt_pkg.init()
cache = apt_pkg.Cache(progress=None)
policy = apt_pkg.Policy(cache)
#policy.create_pin('origin', '', 'Debian', -1)
policy.create_pin('origin', 'apt', 'Debian', -1)
policy.init_defaults()

print([ (v, policy.get_priority(v)) for v in cache['apt'].version_list ])


All calls to get_priority return 500---not -1, as I am trying to get here.

I must be doing something silly.  I'd appreciate any help.

Best,
Antonio