Does this make a difference?

```bash
% grep -r pip_cache       
nova/chef/data_bags/crowbar/bc-template-nova.schema:            "use_pip_cache": { "type": "bool", "required": true },
nova/chef/data_bags/crowbar/bc-template-nova.json:      "use_pip_cache": false,
heat/chef/data_bags/crowbar/bc-template-heat.schema:            "use_pip_cache": { "type": "bool", "required": true },
heat/chef/data_bags/crowbar/bc-template-heat.json:      "use_pip_cache": false,
neutron/chef/data_bags/crowbar/bc-template-neutron.schema:                    "use_pip_cache": { "type": "bool", "required": true },
neutron/chef/data_bags/crowbar/bc-template-neutron.json:      "use_pip_cache": true,
nova_dashboard/chef/data_bags/crowbar/bc-template-nova_dashboard.schema:            "use_pip_cache": { "type": "bool", "required": true },
nova_dashboard/chef/data_bags/crowbar/bc-template-nova_dashboard.json:      "use_pip_cache": true,
keystone/chef/data_bags/crowbar/bc-template-keystone.json:      "use_pip_cache": true,
keystone/chef/data_bags/crowbar/bc-template-keystone.schema:                    "use_pip_cache": { "type": "bool", "required": true },
cinder/chef/data_bags/crowbar/bc-template-cinder.schema:            "use_pip_cache": { "type": "bool", "required": true },
cinder/chef/data_bags/crowbar/bc-template-cinder.json:      "use_pip_cache": true,
ceilometer/chef/data_bags/crowbar/bc-template-ceilometer.schema:            "use_pip_cache": { "type": "bool", "required": true },
ceilometer/chef/data_bags/crowbar/bc-template-ceilometer.json:      "use_pip_cache": true,
quantum/chef/data_bags/crowbar/bc-template-quantum.json:      "use_pip_cache": false,
quantum/chef/data_bags/crowbar/bc-template-quantum.schema:                    "use_pip_cache": { "type": "bool", "required": true },
glance/chef/data_bags/crowbar/bc-template-glance.schema:            "use_pip_cache": { "type": "bool", "required": true },
glance/chef/data_bags/crowbar/bc-template-glance.json:      "use_pip_cache": true,
barclamp-ceilometer/chef/data_bags/crowbar/bc-template-ceilometer.schema:            "use_pip_cache": { "type": "bool", "required": true },
barclamp-ceilometer/chef/data_bags/crowbar/bc-template-ceilometer.json:      "use_pip_cache": true,
swift/chef/cookbooks/swift/recipes/proxy.rb:      pip_cmd = "pip install --index-url http://#{provisioner_addr}:#{provisioner_port}/files/pip_cache/simple/"
swift/chef/data_bags/crowbar/bc-template-swift.schema:            "use_pip_cache": { "type": "bool", "required": true },
swift/chef/data_bags/crowbar/bc-template-swift.json:      "use_pip_cache": true,
```