Method for sending the registration Email to the user

def send_email(self, register_user):
        """
            Method for sending the registration Email to the user
        """
        try:
            from flask_mail import Mail, Message
        except Exception:
            log.error("Install Flask-Mail to use User registration")
            return False
        mail = Mail(self.appbuilder.get_app)
        msg = Message()
        msg.subject = self.email_subject
        url = url_for(
            ".activation",
            _external=True,
            activation_hash=register_user.registration_hash,
        )
        msg.html = self.render_template(
            self.email_template,
            url=url,
            username=register_user.username,
            first_name=register_user.first_name,
            last_name=register_user.last_name,
        )
        msg.recipients = [register_user.email]
        try:
            mail.send(msg)
        except Exception as e:
            log.error("Send email exception: {0}".format(str(e)))
            return False
        return True