To Test:
  * Follow the testing instructions in bug 440418, but put both your shadow and  
    non-shadow channel in the rhn_channel field for the errata_files.
  * Now, when you run rhn-migrate-channel-internal, it should error out, saying 
    that there are duplicate packages in the channels, and giving the path to the 
    duplicates.

4/7/08--detects duplicate pack-- all set in dev
Migrating content for rhel-i386-server-5-shadow to rhel-i386-server-5

Error Message:
    --force-packages not specified and some duplicate packages exist in the real
channel:
rhn/public/NULL/seamonkey-nspr-devel/1.0.9-0.16.el3/i386/seamonkey-nspr-devel-1.0.9-0.16.el3.i386.rpm
Error Class Code: 36
Error Class Info: Invalid action
Explanation: 
     An error has occurred while processing your request. If this problem
     persists please enter a bug report at bugzilla.redhat.com.
     If you choose to submit the bug report, please be sure to include
     details of what you were trying to do when this error occurred and
     details on how to reproduce this problem.

Verified

Finally! Man that was annoying to test.