Netty classes are published under artifacts with different names, so our build needs to exclude the org.jboss.netty:netty versions of the Netty artifact. However, our existing exclusions were incomplete, leading to situations where duplicate Netty classes would wind up on the classpath and cause compile errors (or worse).
We should fix this and should also start using Maven Enforcer's dependency banning mechanisms to prevent this problem from ever being reintroduced.