This is Ubuntu 16.04
In this file

sudo nano /etc/apache2/mods-available/alias.conf

The file look like this:

<IfModule alias_module>
 # Aliases: Add here as many aliases as you need (with no limit). The format is
 # Alias fakename realname
 #
 # Note that if you include a trailing / on fakename then the server will
 # require it to be present in the URL. So "/icons" isn't aliased in this
 # example, only "/icons/". If the fakename is slash-terminated, then the
 # realname must also be slash terminated, and if the fakename omits the
 # trailing slash, the realname must also omit it.
 #
 # We include the /icons/ alias for FancyIndexed directory listings. If
 # you do not use FancyIndexing, you may comment this out.

 Alias /icons/ "/usr/share/apache2/icons/"

 <Directory "/usr/share/apache2/icons">
 Options FollowSymlinks
 AllowOverride None
 Require all granted
 </Directory>

</IfModule>

I just added hash #

#Alias /icons/ "/usr/share/apache2/icons/"