The standard validation.xml document generated to META-INF needs the second term of the xsi:schemaLocation to be a full URL. The currently generated xml is invalid and is flagged by eclipse Neon.3 with a warning message. It should be

xsi:schemaLocation="http://jboss.org/xml/ns/javax/validation/configuration http://www.jboss.org/xml/ns/javax/validation/configuration/validation-configuration-1.1.xsd"

See https://developer.jboss.org/message/971951#971951