Bug#918299: python-oslo.messaging build depends on python-pyngus that is currently not in buster

[Adrian Bunk]

Source: python-oslo.messaging
Version: 8.1.0-3
Severity: serious
Tags: ftbfs
Control: block -1 by 896117 896507 897841

python-oslo.messaging build depends on python-pyngus that is currently
not in buster due to #896117, #896507 and #897841.