openSUSE Leap 15.1, rabbitmq-server-3.7.23-lp151.150.1.x86_64 from
software.opensuse.org / Distribution: Cloud:OpenStack:Master

When running RabbitMQ on clustered control nodes, the according resource agent
will report the following during each monitoring cycle (i.e. every 30 seconds):

Feb  4 17:15:31 controller01 pacemaker-execd[2291]: message repeated 3 times: [
 notice: rabbitmq_monitor_27000:14534:stderr [ warning: the VM is running with
native name encoding of latin1 which may cause Elixir to malfunction as it
expects utf8. Please ensure your locale is set to UTF-8 (which can be verified
by running "locale" in your shell) ]]

Pacemaker runs the agent with "LC_ALL=C", so the warning about non-UTF-8 is
correct.

Changing the agent, to set "C.utf-8", corrects the situation:

--- cut here ---
controller01:/usr/lib/ocf/resource.d/rabbitmq # diff -C 5
rabbitmq-server-ha.dist rabbitmq-server-ha
*** rabbitmq-server-ha.dist     2020-02-05 11:01:13.146055039 +0100
--- rabbitmq-server-ha  2020-02-04 17:15:43.559636418 +0100
***************
*** 20,29 ****
--- 20,31 ----
  # Initialization:

  : ${OCF_FUNCTIONS_DIR=${OCF_ROOT}/lib/heartbeat}
  . ${OCF_FUNCTIONS_DIR}/ocf-shellfuncs

+ LC_ALL="C.utf-8"
+ 
  #######################################################################

  # Fill in some defaults if no values are specified

  PATH=/sbin:/usr/sbin:/bin:/usr/bin
controller01:/usr/lib/ocf/resource.d/rabbitmq #
--- cut here ---

Running the modified agent has not shown any negative side effects.