localhost / userdir on macOS Sierra

There is an updated tutorial here: How to Set up Apache in macOS Sierra 10.12

It includes extra configurations like uncommenting the following lines by removing the "#":

#LoadModule userdir_module libexec/apache2/mod_userdir.so
...
#LoadModule vhost_alias_module libexec/apache2/mod_vhost_alias.so
...
#Include /private/etc/apache2/extra/httpd-userdir.conf
...
#Include /private/etc/apache2/extra/httpd-vhosts.conf

in /etc/apache2/httpd.conf

and uncommenting:

#Include /private/etc/apache2/users/*.conf

in /etc/apache2/extra/httpd-userdir.conf

and restarting apache: sudo apachectl restart

It should work.