Group keys are keys used by all the hosts listening to a specific
topic. The unqualified topic name is the group name.
Example: conductor, scheduler, ...

Change-Id: Ia5bcdd140cef16e07d4d8ab4030d1ac5cb59212c

Wires in SecureMessage so that signing can be optionally used.
Signing messages is always attempted but failing to create a signed message is
currently not fatal. In case of failure the message is sent unsigned.

Once all services has been converted to support signing, we can start switching
on mandatory signing.

Currently the service name needs to be a global due to the way services are
constructed.

Change-Id: Ie565bbaf61a69a4e526e78e723efecb5e2712877

The KDS review process has determined some changes to the API. This patch fixes
KDSClient to interoperate properly.

Change-Id: I888e8a41573f171048356a9d277de1d7610537ce

Fixes H202, H602 errors

Change-Id: Ic3045f15116d1d7a28b63bc94a0a341b9304ffdd

This patch drops the obsolete openstack.common.exception module.

Most project should define their own exception based on their API and
the context they evolve in. Many projects don't use this, only neutron,
cinder and heat used it. I've copy pasted the few exceptions that they
were using, but that's still by far less code than this whole file.
Ultimately that will let them a chance to remove or shring their own
exception.py. I don't think most projects should have one anyway.

Change-Id: Ia8b2b29bd443233def324e97de7342c2634bccff
Closes-Bug: #1208734