code: 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()