$ mvn clean validate | head -n 15
[INFO] Scanning for projects...
[WARNING]
[WARNING] Some problems were encountered while building the effective model for org.wildfly.core:wildfly-core-testbom:pom:30.0.0.Beta1-SNAPSHOT
[WARNING] 'build.pluginManagement.plugins.plugin.(groupId:artifactId)' must be unique but found duplicate declaration of plugin org.apache.maven.plugins:maven-gpg-plugin @ org.wildfly.core:wildfly-core-parent:30.0.0.Beta1-SNAPSHOT, /home/yborgess/dev/projects/wildfly-core/pom.xml, line 384, column 25
[WARNING]
[WARNING] Some problems were encountered while building the effective model for org.wildfly.core:wildfly-core-parent:pom:30.0.0.Beta1-SNAPSHOT
[WARNING] 'build.pluginManagement.plugins.plugin.(groupId:artifactId)' must be unique but found duplicate declaration of plugin org.apache.maven.plugins:maven-gpg-plugin @ line 384, column 25
[WARNING]
[WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
[WARNING]
[WARNING] For this reason, future Maven versions might no longer support building such malformed projects.
[WARNING]
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Build Order:
[INFO]