test.write('SConstruct', """
import SCons.Defaults
env = Environment()
-env['BUILDERS']['B'] = Builder(action='%s build.py $TARGET $SOURCES')
+env['BUILDERS']['B'] = Builder(action=r'%s build.py $TARGET $SOURCES')
env.B(target = 'sub1/foo.out', source = 'sub1/foo.in')
Default('.')
Export('env')