Error executing action `create` on resource 'user[Webserver user and group]'

who can tell me why ?

i get the all answers are change the user and group by adding the following lines to /etc/gitlab/gitlab.rb user['username'] = "gitlab" user['group'] = "gitlab"

and then Run sudo gitlab-ctl reconfigure for the change to take effect.

but i try it ,nothing to do; So i need help ,thanks!