def prepare(self):
        if self.depends is not None:
            for d in self.depends:
                if d.missing():
                    msg = "Explicit dependency `%s' not found, needed by target `%s'."
                    raise SCons.Errors.StopError(msg % (d, self))
        if self.implicit is not None:
            for i in self.implicit:
                if i.missing():
                    msg = "Implicit dependency `%s' not found, needed by target `%s'."
                    raise SCons.Errors.StopError(msg % (i, self))
        self.binfo = self.get_binfo()