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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def auth_user_remote_user(self, username):
 """ REMOTE_USER user Authentication :param username: user's username for remote auth :type self: User model """

        user = self.find_user(username=username)

        # User does not exist, create one if auto user registration.
        if user is None and self.auth_user_registration:
            user = self.add_user(
                # All we have is REMOTE_USER, so we set
                # the other fields to blank.
                username=username,
                first_name=username,
                last_name="-",
                email="-",
                role=self.find_role(self.auth_user_registration_role),
            )

        # If user does not exist on the DB and not auto user registration,
        # or user is inactive, go away.
        elif user is None or (not user.is_active):
            log.info(LOGMSG_WAR_SEC_LOGIN_FAILED.format(username))
            return None

        self.update_user_auth_stat(user)
        return user