def Command(self, target, source, action, **kw):
        """Builds the supplied target files from the supplied
        source files using the supplied action.  Action may
        be any type that the Builder constructor will accept
        for an action."""
        bkw = {
            'action' : action,
            'target_factory' : self.fs.Entry,
            'source_factory' : self.fs.Entry,
        }
        try: bkw['source_scanner'] = kw['source_scanner']
        except KeyError: pass
        else: del kw['source_scanner']
        bld = SCons.Builder.Builder(**bkw)
        return bld(self, target, source, **kw)
Builds the supplied target files from the supplied
        source files using the supplied action.  Action may
        be any type that the Builder constructor will accept
        for an action.