Method import_zmq returns None if can't import zmq module.
For runtime code, an ImportError is raised, and for tests,
a skip message "zmq not available" is sent, so it's unnecessary
to log error which shows up in other projects' unit test logs.
Co-Authored-By: Oleksii Zamiatin <ozamiatin@mirantis.com>
Change-Id: Iebf15042f45da56eb633a0a70822c487dc72c884
Closes-Bug: #1528415