ant - Build Jython Err: "NoClassDefFoundError: org/antlr/Tool" -

i tried build jython on macbook pro, got error after simpley ant command.

$ jython-2.5.4-rc1-sources zzhao$ ant buildfile: /users/jack/dev/jython/jython-2.5.4-rc1-sources/build.xml  init:  needed-check:  clean-if-antlr-needed:  init:  clean-checkout-dir:  clean:  prepare-output:     [mkdir] created dir: /users/jack/dev/jython/jython-2.5.4-rc1-sources/build/classes     [mkdir] created dir: /users/jack/dev/jython/jython-2.5.4-rc1-sources/build/gensrc/org/python/antlr     [mkdir] created dir: /users/jack/dev/jython/jython-2.5.4-rc1-sources/build/exposed     [mkdir] created dir: /users/jack/dev/jython/jython-2.5.4-rc1-sources/dist  antlr_gen:      [java] exception in thread "main" java.lang.noclassdeffounderror: org/antlr/tool      [java] caused by: java.lang.classnotfoundexception: org.antlr.tool      [java]     @ java.net.urlclassloader$1.run(urlclassloader.java:202)      [java]     @ java.security.accesscontroller.doprivileged(native method)      [java]     @ java.net.urlclassloader.findclass(urlclassloader.java:190)      [java]     @ java.lang.classloader.loadclass(classloader.java:306)      [java]     @ sun.misc.launcher$appclassloader.loadclass(launcher.java:301)      [java]     @ java.lang.classloader.loadclass(classloader.java:247)  build failed /users/jack/dev/jython/jython-2.5.4-rc1-sources/build.xml:496: java returned: 1 

any idea problem?

your build failing in "antlr_gen" target. java task missing antlr jar classpath.

can't further without ant build.xml debug.