GitLab Error: Error executing action `create` on resource 'group[gitlab-www]'

I am getting this error while running gitlab reconfigure command as a root user

gitlab-ctl reconfigure

I am using Oracle Linux 6,  Below is the log:
Converging 265 resources


* directory[/etc/gitlab] action nothing (skipped due to action :nothing)
  * directory[/var/opt/gitlab] action create (up to date)
  * directory[/opt/gitlab/embedded/etc] action create (up to date)
  * template[/opt/gitlab/embedded/etc/gitconfig] action create (up to date)
Recipe: gitlab::web-server
  * group[gitlab-www] action create

================================================================================
Error executing action `create` on resource 'group[gitlab-www]'
================================================================================

Chef::Exceptions::Exec
----------------------
groupadd gitlab-www -r returned 4, expected 0

Resource Declaration:
---------------------
# In /opt/gitlab/embedded/cookbooks/cache/cookbooks/gitlab/definitions/account.rb

 26:     group groupname do
 27:       gid params[:gid]
 28:       system params[:system]
 29:       if params[:append_to_group]
 30:         append true
 31:         members params[:group_members]
 32:       end
 33:       action params[:action]

Compiled Resource:
------------------
# Declared in /opt/gitlab/embedded/cookbooks/cache/cookbooks/gitlab/definitions/account.rb:26:in `block in from_file'

group("gitlab-www") do
  params {:action=>nil, :username=>"gitlab-www", :uid=>nil, :ugid=>"gitlab-www", :groupname=>"gitlab-www", :gid=>nil, :shell=>"/bin/false", :home=>"/var/opt/gitlab/nginx", :system=>true, :append_to_group=>false, :group_members=>[], :user_supports=>{:manage_home=>false}, :manage=>true, :name=>"Webserver user and group"}
  action [:create]
  retries 0
  retry_delay 2
  default_guard_interpreter :default
  group_name "gitlab-www"
  declared_type :group
  cookbook_name "gitlab"
  recipe_name "web-server"
  system true
end


Running handlers:
[2016-04-22T00:01:52-07:00] ERROR: Running exception handlers
Running handlers complete
[2016-04-22T00:01:52-07:00] ERROR: Exception handlers complete
Chef Client failed. 0 resources updated in 43 seconds
[2016-04-22T00:01:52-07:00] FATAL: Stacktrace dumped to /opt/gitlab/embedded/cookbooks/cache/chef-stacktrace.out
[2016-04-22T00:01:52-07:00] ERROR: group[gitlab-www] (gitlab::web-server line 26) had an error: Chef::Exceptions::Exec: groupadd gitlab-www -r returned 4, expected 0
[2016-04-22T00:01:53-07:00] FATAL: Chef::Exceptions::ChildConvergeError: Chef run process exited unsuccessfully (exit code 1)

Note :<.b> I  tried to add

user['username'] = "gitlab"
user['group'] = "gitlab"
in /etc/gitlab/gitlab.rb   but did not help.

Please suggest any solution. Thanks