--- a/build.xml.orig	2015-06-27 16:12:08.442000000 +0000
+++ b/build.xml	2015-06-27 16:12:15.684000000 +0000
@@ -448,7 +448,7 @@
     </target>
 
     <target name="antlr_gen" depends="prepare-output" unless="antlr.notneeded">
-        <java classname="org.antlr.Tool" failonerror="true" fork="true" dir="${jython.base.dir}">
+        <java classname="org.antlr.Tool" failonerror="false" fork="true" dir="${jython.base.dir}">
             <jvmarg value="-Xmx512m"/>
             <arg value="-Xconversiontimeout"/>
             <arg value="2000"/>