class Login(Handler):
    """Renders Login page and makes user cookie"""
    def get(self):
        self.render("login.html")

    def post(self):
        self.username = self.request.get("username")
        self.password = self.request.get("password")
        user = User.gql("WHERE username = '%s'" % username).get()
        if user and valid_pw(username, password, user.pw_hash):
            user_cookie = make_secure_val(str(self.username))
            self.response.headers.add_header("Set-Cookie", "user=%s; Path=/" % user_cookie)
            self.redirect("/welcome")
        else:
            error = "Not a valid username or password"
            self.render("login.html", username = self.username, error = error)