upgrade to maven-3.1.0 and java-1.7.0_25
add configuration options "runOnlyAtExecutionRoot" and "failOnError".
 runOnlyAtExecutionRoot – This will cause the assembly to run only at the top of a given module tree. That is, run in the project contained in the same folder where the mvn execution was launched.
 failOnError – Mojo failure will fail build. If false the any errors are simply logged.