Error in TASK [init bench]

in installation i got this error in : TASK [ init bench] :

 [localhost]: FAILED! => {"changed": true, "cmd": ["bench", "init", "/home/frappe/frappe-bench", "--frappe-branch", "develop"], "delta": "0:04:13.246585", "end": "2017-07-15 05:49:49.735687", "failed": true, "rc": 1, "start": "2017-07-15 05:45:36.489102", "stderr": "INFO:bench.utils:virtualenv -q env -p /usr/bin/python\nINFO:bench.utils:./env/bin/pip -q install --upgrade pip\nINFO:bench.utils:./env/bin/pip -q install wheel\nINFO:bench.utils:./env/bin/pip -q install six\n/home/frappe/frappe-bench/env/local/lib/python2.7/site-packages/pip/_vendor/requests/packages/urllib3/util/ssl_.py:318: SNIMissingWarning: An HTTPS request has been made, but the SNI (Subject Name Indication) extension to TLS is not available on this platform. This may cause the server to present an incorrect TLS certificate, which can cause validation failures. You can upgrade to a newer version of Python to solve this. For more information, see https://urllib3.readthedocs.io/en/latest/security.html#snimissingwarning.\n  SNIMissingWarning\n/home/frappe/frappe-bench/env/local/lib/python2.7/site-packages/pip/_vendor/requests/packages/urllib3/util/ssl_.py:122: InsecurePlatformWarning: A true SSLContext object is not available. This prevents urllib3 from configuring SSL appropriately and may cause certain SSL connections to fail. You can upgrade to a newer version of Python to solve this. For more information, see https://urllib3.readthedocs.io/en/latest/security.html#insecureplatformwarning.\n  InsecurePlatformWarning\nINFO:bench.utils:./env/bin/pip -q install -e git+https://github.com/frappe/python-pdfkit.git#egg=pdfkit\nINFO:bench.app:getting app frappe\nINFO:bench.utils:git clone https://github.com/frappe/frappe.git --branch develop  --origin upstream\nCloning into 'frappe'...\nINFO:bench.app:installing frappe\nINFO:bench.utils:/home/frappe/frappe-bench/env/bin/pip install -q  -e /home/frappe/frappe-bench/apps/frappe --no-cache-dir\n/home/frappe/frappe-bench/env/local/lib/python2.7/site-packages/pip/_vendor/requests/packages/urllib3/util/ssl_.py:318: SNIMissingWarning: An HTTPS request has been made, but the SNI (Subject Name Indication) extension to TLS is not available on this platform. This may cause the server to present an incorrect TLS certificate, which can cause validation failures. You can upgrade to a newer version of Python to solve this. For more information, see https://urllib3.readthedocs.io/en/latest/security.html#snimissingwarning.\n  SNIMissingWarning\n/home/frappe/frappe-bench/env/local/lib/python2.7/site-packages/pip/_vendor/requests/packages/urllib3/util/ssl_.py:122: InsecurePlatformWarning: A true SSLContext object is not available. This prevents urllib3 from configuring SSL appropriately and may cause certain SSL connections to fail. You can upgrade to a newer version of Python to solve this. For more information, see https://urllib3.readthedocs.io/en/latest/security.html#insecureplatformwarning.\n  InsecurePlatformWarning\nINFO:bench.utils:npm install\nKilled\nTraceback (most recent call last):\n  File \"/usr/local/bin/bench\", line 11, in <module>\n    load_entry_point('bench', 'console_scripts', 'bench')()\n  File \"/home/frappe/.bench/bench/cli.py\", line 40, in cli\n    bench_command()\n  File \"/usr/local/lib/python2.7/dist-packages/click/core.py\", line 722, in __call__\n    return self.main(*args, **kwargs)\n  File \"/usr/local/lib/python2.7/dist-packages/click/core.py\", line 697, in main\n    rv = self.invoke(ctx)\n  File \"/usr/local/lib/python2.7/dist-packages/click/core.py\", line 1066, in invoke\n    return _process_result(sub_ctx.command.invoke(sub_ctx))\n  File \"/usr/local/lib/python2.7/dist-packages/click/core.py\", line 895, in invoke\n    return ctx.invoke(self.callback, **ctx.params)\n  File \"/usr/local/lib/python2.7/dist-packages/click/core.py\", line 535, in invoke\n    return callback(*args, **kwargs)\n  File \"/home/frappe/.bench/bench/commands/make.py\", line 19, in init\n    verbose=verbose, clone_from=clone_from)\n  File \"/home/frappe/.bench/bench/utils.py\", line 64, in init\n    update_npm_packages(bench_path=path)\n  File \"/home/frappe/.bench/bench/utils.py\", line 432, in update_npm_packages\n    exec_cmd('npm install', cwd=bench_path)\n  File \"/home/frappe/.bench/bench/utils.py\", line 130, in exec_cmd\n    raise CommandFailedError(cmd)\nbench.utils.CommandFailedError: npm install", "stdout": "Already using interpreter /usr/bin/python\n('installing', u'frappe')\nUpdating node libraries...", "stdout_lines": ["Already using interpreter /usr/bin/python", "('installing', u'frappe')", "Updating node libraries..."], "warnings": []}
to retry, use: --limit @develop/install.retry

PLAY RECAP *********************************************************************
localhost : ok=31 changed=20 unreachable=0 failed=1

Traceback (most recent call last):
File “install.py”, line 355, in
install_bench(args)
File “install.py”, line 108, in install_bench
run_playbook(‘develop/install.yml’, sudo=True, extra_vars=extra_vars)
File “install.py”, line 301, 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/install.yml’, ‘-e’, ‘@/tmp/extra_vars.json’, ‘–become’, ‘–become-user=frappe’]’ returned non-zero exit status 2

my server os is : Ubuntu 14.04