Bug#918277: cairocffi build depends on python3-xcffib that is currently not in buster

[Adrian Bunk]

Source: cairocffi
Version: 0.7.2-2.1
Severity: serious
Tags: ftbfs
Control: block -1 by 860739 892648 903619 917171

cairocffi build depends on python3-xcffib that is currently not
in buster due to #860739, #892648, #903619 and #917171.