phpmyadmin on apache2 reload: Unknown Authz provider: valid-user error

After standard installation of phpmyadmin on Ubuntu 14.04 I found <site>/phpmyadmin doesn't work. After googling it, I found this can be solved with adding this line

Include "/etc/apache2/conf-enabled/*.conf"

Added to /etc/apache2/apache2.conf config file.

But after apache reload I get this error message

 * Reloading web server apache2
 * 
 * The apache2 configtest failed. Not doing anything.
Output of config test was:
AH00526: Syntax error on line 30 of /etc/apache2/conf-enabled/phpmyadmin.conf:
Unknown Authz provider: valid-user
Action 'configtest' failed.
The Apache error log may have more information.

How can I fix error and make phpmyadmin working?

It seems that the module 'mod_authz_user' is not enabled. You can use a2enmod to enable it for your apache installation.

sudo a2enmod authz_user

It will now tell you that is has been activated and that you need to restart your apache instance. In Ubuntu 14.04 this can be done as follows:

sudo service apache2 restart