Bug#351056: many packages involved, not just python-twisted

[Andrew Schulman <andrex@alumni.utexas.net>]

> > I run apt-get clean, and then every time I run apt-get
> > dist-upgrade it wants to reinstall the same list of packages.  A.
>
> Does 'apt-cache policy foobar' list a version twice for the packages?

Yes:

$ apt-cache policy screen
screen:
  Installed: 4.0.2-4.1
  Candidate: 4.0.2-4.1
  Version table:
     4.0.2-4.1 0
        300 http://http.us.debian.org unstable/main Packages
     4.0.2-4.1 0
        200 http://amd64.debian.net stable/main Packages
     4.0.2-4.1 0
        990 http://amd64.debian.net testing/main Packages
 *** 4.0.2-4.1 0
        100 /var/lib/dpkg/status

Same for all of the other packages in the list.  So is this apt-get's 
fault, or the package archives?  If it's the package archives, then all 
users with these same lines in their sources.list files should be having 
the same symptoms as me.

Thanks, Andrew.