os_gnocchi pip install failure

gistfile1.txt

TASK: os_gnocchi : Install pip packages (1 retries left).Result was: {
    "attempts": 5,
    "cmd": "/openstack/venvs/gnocchi-untagged/bin/pip2 install -U --constraint /opt/developer-pip-constraints.txt --constraint http://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt --no-binary libvirt-python gnocchi[mysql file swift ceph] keystonemiddleware gnocchiclient python-memcached pycrypto",
    "failed": true,
    "invocation": {
        "module_args": {
            "chdir": null,
            "editable": true,
            "executable": null,
            "extra_args": "--constraint /opt/developer-pip-constraints.txt --constraint http://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt --no-binary libvirt-python",
            "name": [
                "gnocchi[mysql",
                "file",
                "swift",
                "ceph] keystonemiddleware gnocchiclient python-memcached pycrypto"
            ],
            "requirements": null,
            "state": "latest",
            "umask": null,
            "use_mirrors": true,
            "version": null,
            "virtualenv": "/openstack/venvs/gnocchi-untagged",
            "virtualenv_command": "virtualenv",
            "virtualenv_python": null,
            "virtualenv_site_packages": false
        },
        "module_name": "pip"
    },
    "msg": "\n:stderr: Ignoring dnspython3: markers 'python_version == \"3.4\"' don't match your environment\nIgnoring dnspython3: markers 'python_version == \"3.5\"' don't match your environment\nInvalid requirement: 'gnocchi[mysql'\nTraceback (most recent call last):\n  File \"/openstack/venvs/gnocchi-untagged/local/lib/python2.7/site-packages/pip/req/req_install.py\", line 82, in __init__\n    req = Requirement(req)\n  File \"/openstack/venvs/gnocchi-untagged/local/lib/python2.7/site-packages/pip/_vendor/packaging/requirements.py\", line 96, in __init__\n    requirement_string[e.loc:e.loc + 8]))\nInvalidRequirement: Invalid requirement, parse error at \"'[mysql'\"\n\n",
    "retries": 6