Bug#638024: [apt] APT::Default-Release considers equivalent suite names differently ("testing" != "wheezy")

[E Taylor <hagfish@hagfish.name>]

I encountered this bug (or something similar) recently as part of my
preparations of upgrading to "jessie".  My sources.list was pointing to
"testing" so I changed it, using Synaptic, to point to "wheezy".  After
applying a large number of updates and rebooting, I tried using Synaptic
again and was greeted with the message:

    The value 'testing' is invalid for APT::Default-Release as such a
release is not available in the sources

Closing this dialog box caused Synaptic itself to close.  I then found
this bug report, but the advice here was not enough to get Synaptic
working again, so I searched wider on the web and found this page:

   
http://www.kubuntuforums.net/showthread.php?61484-Upgrade-from-Percise-results-in-bug!

This lead to me using a workaround of editing
/root/.synaptic/synaptic.conf and changing the last configuration option
from:

    DefaultDistro "testing";

to:

    DefaultDistro "wheezy";

After this, Synaptic loaded without an error message.

I don't know if this information highlights a bug in Synaptic, or a
workaround for bug 638024, but if anyone else encounters this problem
and finds this page, hopefully my comment will prove helpful to them.

Best regards,
Edwin Taylor