abuild silently fails if $builddir does not exist
$builddir is set to a directory that does not exist, abuild silently fails and keeps using the default build directory. This is confusing as you might not always realise that you have made a typo and end up spending time trying to debug something that makes no sense. It would be preferable if abuild failed and said that
$builddir does not exist.
Another similar issue is that abuild also silently fails if
$builddir points to a file (and not a directory).