<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def install_required(f):
 """ Return an exception if the namespace is not already installed """


    @wraps(f)
    def wrapped(self, *args, **kwargs):
        if self.directory.new:
            raise SprinterException("Namespace %s is not yet installed!" % self.namespace)
        return f(self, *args, **kwargs)
    return wrapped