Use module.warn() instead of returning warnings
SUMMARY
Returning warnings as warnings has been deprecated.
Ref: #635.
ISSUE TYPE
Bugfix Pull Request
COMPONENT NAME
firewalld_info
mount
Reviewed-by: Hideki Saito <saito@fgrep.org>
(cherry picked from commit 6da1331018)
Co-authored-by: softwarefactory-project-zuul[bot] <33884098+softwarefactory-project-zuul[bot]@users.noreply.github.com>
