Support list queue pagination in transport.

Change-Id: I65c553c64797dc2a8193c6af13fef97c95f7bebf
Implements: blueprint transport-wsgi
A helper to remove None value entries from a dict.

Change-Id: I414951124b52f8c96a1aebacaec61f05fef8ef67
Switch to flake8 and fix errors.

Change-Id: I185d0841c0b3400c47e30f9398634f36e78a684e