Comment 2 for bug 1820033

Reviewed: https://review.openstack.org/643263
Committed: https://git.openstack.org/cgit/openstack/ospurge/commit/?id=8a69363f8e00b047f89c74f5a0a89d218f868a42
Submitter: Zuul
Branch: master

commit 8a69363f8e00b047f89c74f5a0a89d218f868a42
Author: Yves-Gwenael Bourhis <email address hidden>
Date: Thu Mar 14 10:39:37 2019 +0100

    Fix test_get_resource_classes parameter passing

    In utils.get_resource_classes we expect a list of strings.
    However we are passing a string.
    The test was succeding by pure luck.
    If we pass something else (such as 'Stacks') we had multiple results.
    This test was confusing for other developers implementing other tests.

    Closes-Bug: #1820033

    Change-Id: I8414b7582d94b199457a01e4916a7e7b6e51edbc