Since driver version 3.0 MariaDB introduced new logging system to the driver that is based on Slf4j. This dependency is optional, but in case that the slf4j classes aren't available, the log messages are written to stderr which are then caught up by EAP and logged as ERROR even though it should be for example WARN.
The code can be seen here: https://github.com/mariadb-corporation/mariadb-connector-j/blob/master/src/main/java/org/mariadb/jdbc/util/log/Loggers.java#LL98C52-L98C52

To avoid this problem the jdbc driver module should have the dependency to org.slf4j module.
This doesn't have any implications to the implementation but we should have this documented somewhere. The most straightforward place for this seems to be something like this: https://access.redhat.com/documentation/en-us/red_hat_jboss_enterprise_application_platform/7.4/html-single/configuration_guide/index#example_mariadb_datasource