rabbitmq-server: chown: unknown user/group @RABBITMQ_USER@:@RABBITMQ_GROUP@

When enabling the management plugin, there is an error that chown can't find the user/group.

# rabbitmq-plugins enable rabbitmq_management
Enabling plugins on node rabbit@tbrabbit:
rabbitmq_management
The following plugins have been configured:
  rabbitmq_management
  rabbitmq_management_agent
  rabbitmq_web_dispatch
Applying plugin configuration to rabbit@tbrabbit...
The following plugins have been enabled:
  rabbitmq_management
  rabbitmq_management_agent
  rabbitmq_web_dispatch

started 3 plugins.
chown: unknown user/group @RABBITMQ_USER@:@RABBITMQ_GROUP@

Apparently, the shell script rabbitmq-plugins at line 40 is trying to chown the erlang cookie, but the variables for user/group are not set properly:

maybe_fixup_erlang_cookie() {
    # rabbitmq/rabbitmq-server-release#85
    _rabbitmq_home="$(cd ~rabbitmq && pwd)"
    _erlang_cookie="$_rabbitmq_home/.erlang.cookie"
    if [ -f "$_erlang_cookie" ]
    then
        chown @RABBITMQ_USER@:@RABBITMQ_GROUP@ "$_erlang_cookie"
        chmod 400 "$_erlang_cookie"
    fi
}

A quick grep shows the same variables under the following files:

# grep -ri '@RABBITMQ_USER@' /usr/sbin
/usr/sbin/rabbitmq-server:        chown @RABBITMQ_USER@:@RABBITMQ_GROUP@ "$_erlang_cookie"
/usr/sbin/rabbitmq-plugins:        chown @RABBITMQ_USER@:@RABBITMQ_GROUP@ "$_erlang_cookie"
/usr/sbin/rabbitmqctl:        chown @RABBITMQ_USER@:@RABBITMQ_GROUP@ "$_erlang_cookie"

Thank you.