Comment 5 for bug 1577731

The issue occurs only if the value starts with "$" character. The workaround is to escape it.

From Shaker perspective it's possible to fix this by escaping "$" before setting it as default to config option (http://git.openstack.org/cgit/openstack/shaker/tree/shaker/engine/config.py#n92). Personally, I'd prefer oslo-config to be responsible for reading option values from environment variables and thus doing all magic under the hood.