Comment 4 for bug 1529355

Confirmed the patch fixes the issue.

Without it /var/log/apache2/access.log reports this:
[Fri Nov 23 19:41:07.575706 2018] [authz_core:error] [pid 4855:tid 140320138327808] [client 10.0.100.1:56824] AH02305: no alias provider found for 'blacklisted-ips' (BUG?)

Simple config:
root@trusty-apache:/etc/apache2# cat conf-enabled/authorized.conf
<AuthzProviderAlias ip blacklisted-ips "10.0.100.1 10.10.0.50">
</AuthzProviderAlias>

And to the default vhost, I added this:
 <Directory "/var/www/html">
     <RequireAll>
         Require not blacklisted-ips
         Require all granted
     </RequireAll>
 </Directory>