Comment 3 for bug 1443224

Hi,
I was trying to reproduce your issue:

mkdir -p /var/www/localized-error-pages/
cp /usr/share/apache2/error/include/* /var/www/localized-error-pages/
*made a slight change to the bottom.html in there so I recognize the localized error.

Uncommenting and adapting in /etc/apache2/conf-available/localized-error-pages.conf:
Alias /error/include/ "/var/www/localized-error-pages/"
+ uncommenting the later 37 lines

I access non existing files and see in /var/log/apache2/access.log that the access works.
When accessing a non existent file it didn't cause the same error, but then it didn't show me a localized error either.
So it seems I failed to reproduce your issue because I can't figure out a missing step :-/

But
I experimented a bit and actually
So the default config in /etc/apache2/apache2.conf has:
<Directory /var/www/>
        Options Indexes FollowSymLinks
        AllowOverride None
        Require all granted
</Directory>

And this should already cover /var/www/localized-error-pages/ to be accessible by the server.
Of course not by the browser directly as the document root goes to /var/www/html but I think it should be includable.

Did you set up a custom dir other than /var/www on your system?