Afterstep has a dependency on aterm, this package has been dropped by the rxvt-unicode source package,
it is still present in unstable as a cruft package but is completely gone from testing.

The dependency on aterm has an alternative of x-terminal-emulator, so the package is still installable
but nevertheless leaving which terminal is installed up to luck is less than ideal. Please consider
changing the dependency from eterm to rxvt-unicode (or whatever terminal you deem most appropriate)