repo_build cannot refer to variables in Creating OSA requirement wheels

[Steve Lewis]

Background:
Gnocchi's setup.py allows storage driver choice to customize requirements.
This allows us to only install the additional libraries required for the storage drivers we care about (file, swift, ceph,...).
This should allow us to do the following in role defaults:

gnocchi_pip_packages:
  - "gnocchi[mysql,{{ gnocchi_storage_driver }}]"
  - keystonemiddleware
  - gnocchiclient
  - python-memcached

Where {{ gnocchi_storage_driver }} is defined in the scope of the repo_build role, either through group_vars or an entry
in the user_*.yml files.

Expected:
The repo should build wheels and venvs.

Actual:
During repo_build there is incomplete interpretation occurring when this detail is extracted from the os_roles.

> root@host:/opt/openstack-ansible/playbooks# openstack-ansible repo-build.yml -e repo_build_venv_force_rebuild=true -e gnocchi_storage_driver=file

TASK: [repo_build | Create OpenStack-Ansible requirement wheels] **************
failed: [aio1_repo_container-6e4b000f] => {"changed": true, "cmd": "pip wheel --timeout 120 --wheel-dir /tmp/openstack-wheel-output --find-links /tmp/openstack-wheel-output --constraint /var/www/repo/os-releases/master/requirements_constraints.txt --index-url https://rpc-repo.rackspace.com/pools --trusted-host rpc-repo.rackspace.com --extra-index-url https://pypi.python.org/simple --trusted-host pypi.python.org --build /tmp/openstack-builder --log /var/log/repo/repo_builder.log --requirement /var/www/repo/os-releases/master/requirements_local_filtered.txt", "delta": "0:00:01.263887", "end": "2016-03-15 17:31:45.641337", "rc": 1, "start": "2016-03-15 17:31:44.377450", "warnings": []}
stderr: Ignoring dnspython3: markers "python_version=='3.4'" don't match your environment
Ignoring os-win: markers "python_version=='3.4'" don't match your environment
Ignoring python-ironic-inspector-client: markers "python_version=='3.4'" don't match your environment
Ignoring requestsexceptions: markers "python_version=='3.4'" don't match your environment
Invalid requirement: 'gnocchi[mysql,{# gnocchi_storage_driver'
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/pip/req/req_install.py", line 76, in __init__
    req = pkg_resources.Requirement.parse(req)
  File "/usr/local/lib/python2.7/dist-packages/pip/_vendor/pkg_resources/__init__.py", line 3036, in parse
    req, = parse_requirements(s)
  File "/usr/local/lib/python2.7/dist-packages/pip/_vendor/pkg_resources/__init__.py", line 2976, in parse_requirements
    DISTRO, CBRACKET, line, p, (1,), "'extra' name"
  File "/usr/local/lib/python2.7/dist-packages/pip/_vendor/pkg_resources/__init__.py", line 2945, in scan_list
    raise RequirementParseError(msg, line, "at", line[p:])
RequirementParseError: Expected 'extra' name in gnocchi[mysql,{# gnocchi_storage_driver at {# gnocchi_storage_driver

Workaround:
Roles can install all optional libraries all the time:

gnocchi_pip_packages:
  - "gnocchi[mysql,file,swift,ceph]"
  - keystonemiddleware
  - gnocchiclient
  - python-memcached

[Jonathan Rosser (jrosser)]

The repo_build process is no longer present and all supported releases take a different approach.