Ant configuration fails to find junit.

[Boskovits]

All pacakges using junit fails to build on wip-change-default-java8.
Example error message:
BUILD FAILED
/tmp/guix-build-java-bsh-2.0b6.drv-0/beanshell-2.0b6/build.xml:654: Problem: failed to create task or type junit
Cause: the class org.apache.tools.ant.taskdefs.optional.junit.JUnitTask was not found.
This looks like one of Ant's optional components.
Action: Check that the appropriate optional JAR exists in
-/gnu/store/6lzf3cp16m0xgwr00lymqd3v6fgpvzxv-ant-1.10.1/lib
-/.ant/lib
-a directory added on the command line with the -lib argument

Do not panic, this is a common problem.
The commonest cause is a missing JAR.

This is not a bug; it is a configuration problem

[Boskovits]

It seems, that by adding java-junit and ant-junit to native inputs fixes this.