httpunit version 1.7+dfsg-8 failed to build with openjdk-7

During a rebuild test on precise with default-jdk switched to openjdk-7, a build failure was detected for httpunit version 1.7+dfsg-8.

See attached log for full build failure details.

This log snippet might also be of interest:

 debian/rules build
dh --with javahelper --with jh_maven_repo_helper build
   dh_testdir
   dh_auto_configure
   jh_linkjars
   debian/rules override_dh_auto_build
make[1]: Entering directory `/«BUILDDIR»/httpunit-1.7+dfsg'
ant dist
Buildfile: /«BUILDDIR»/httpunit-1.7+dfsg/build.xml

check_jars_dir:

prepare_local_classpath:
     [echo] using local classpath

prepare_repository_classpath:

prepare:
    [mkdir] Created dir: /«BUILDDIR»/httpunit-1.7+dfsg/build

check_for_optional_packages:

compile-for-java2:

compile:
    [mkdir] Created dir: /«BUILDDIR»/httpunit-1.7+dfsg/build/classes
    [javac] /«BUILDDIR»/httpunit-1.7+dfsg/build.xml:136: warning: 'includeantruntime' was not set, defaulting to build.sysclasspath=last; set to false for repeatable builds
    [javac] Compiling 195 source files to /«BUILDDIR»/httpunit-1.7+dfsg/build/classes
    [javac] /«BUILDDIR»/httpunit-1.7+dfsg/src/com/meterware/httpunit/HttpWebResponse.java:92: error: unmappable character for encoding ASCII
    [javac] // by Roger Lindsj?
    [javac] ^
    [javac] /«BUILDDIR»/httpunit-1.7+dfsg/src/com/meterware/servletunit/ServletUnitServletContext.java:119: error: unmappable character for encoding ASCII
    [javac] // by Timo Westk?mper
    [javac] ^
    [javac] 2 errors

BUILD FAILED
/«BUILDDIR»/httpunit-1.7+dfsg/build.xml:136: Compile failed; see the compiler error output for details.

Total time: 2 seconds
make[1]: *** [override_dh_auto_build] Error 1
make[1]: Leaving directory `/«BUILDDIR»/httpunit-1.7+dfsg'
make: *** [build] Error 2
dpkg-buildpackage: error: debian/rules build gave error exit status 2
────────────────────────────────────────────────────────────────────────────────
Build finished at 20111110-1828

Finished
────────

E: Build failure (dpkg-buildpackage died)