Exclude generated sources from error-prone

Change-Id: I1745ea671de309d76e140d7881eb8ed51eeed4a0

pom.xml

diff --git a/pom.xml b/pom.xml
index f3c0622..fb7a4ba 100644
--- a/pom.xml
+++ b/pom.xml
@@ -388,6 +388,7 @@
           <showWarnings>true</showWarnings>
           <compilerArgs>
             <arg>-Xlint:deprecation</arg>
+            <arg>-XepExcludedPaths:.*/gwtorm/target/generated-sources/.*/.*</arg>
           </compilerArgs>
           <source>${java.version}</source>
           <target>${java.version}</target>