Ubuntu 14.04 installation error

Hii ERPNext Comminity,
I am trying to install ERPNext in Ubuntu14.04
Following error I got
Please help

[WARNING]: Host file not found: /etc/ansible/hosts

[WARNING]: provided hosts list is empty, only localhost is available

PLAY [localhost] ***************************************************************

TASK [Gathering Facts] *********************************************************
ok: [localhost]

TASK [Create user] *************************************************************
fatal: [localhost]: FAILED! => {“changed”: false, “failed”: true, “msg”: “useradd: Permission denied.\nuseradd: cannot lock /etc/passwd; try again later.\n”, “name”: “frappe”, “rc”: 1}
to retry, use: --limit @/tmp/.bench/playbooks/develop/create_user.retry

PLAY RECAP *********************************************************************
localhost : ok=1 changed=0 unreachable=0 failed=1

Traceback (most recent call last):
File :install.py", line 386, in
File :install.py, line 96, in install_bench
run_playbook(‘develop/create_user.yml’, extra_vars=extra_vars)
File :install.py", line 324, in run_playbook
success = subprocess.check_call(args, cwd=os.path.join(cwd, ‘playbooks’))
File “/usr/lib/python2.7/subprocess.py”, line 540, in check_call
raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command ‘[‘ansible-playbook’, ‘-c’, ‘local’, ‘develop/create_user.yml’, ‘-e’, ‘@/tmp/extra_vars.json’]’ returned non-zero exit status 2