guava: ClassPath.getTopLevelClasses() returns empty list.

Summary ClassPath.getTopLevelClasses() returns empty list when the path of the classloader contains special characters.

How to reproduce this error

1. Create a packeage with three classes
2. Create the following unit test

    @Test
    public void testMain() throws Exception {
        ClassLoader loader = this.getClass().getClassLoader();
        ClassPath p = ClassPath.from(loader);
        ImmutableSet<ClassPath.ClassInfo> list = p.getTopLevelClasses("testpackage");
        Assert.assertEquals(3, list.size());
    }

1. Copy the whole project to a folder with special characters in its name (like % for example) and execute it.
2. The test will fail. If you copy the project to a folder without special characters in its path the test will pass.