Comment 9 for bug 1564269

I ran into this issue. And it looks my fault for not using a2enmod.

ls -l /etc/apache2/mods-enabled/proxy.load
lrwxrwxrwx 1 root root 38 Nov 11 2014 proxy.load -> /etc/apache2/mods-available/proxy.load

This breaks apache2.postinst:

  target=$(readlink "$link") || true
  ...
  if [ ! -e "/etc/apache2/mods-enabled/$target" ] ; then

Replacing the symlink targets with relative paths also works around the issue.