Bug#638024: [apt] APT::Default-Release considers equivalent suite
There is another oddity occuring. When an attempt is made to remove a package, the sources are being evaluated and removal of the package is denied:
# apt-get remove epiphany-browser
Reading package lists... Done
E: The value 'squeeze' is invalid for APT::Default-Release as such a release is not available in the sources
For removal of packages, the sources should not be considered and the package should simply be removed.