Controllers of my flask app

controllers.py

import pymysql
from flask import Blueprint, request, render_template, json, Flask
from flask_sqlalchemy import SQLAlchemy
from sqlalchemy import create_engine

from app.users_bundle.models import User
from sqlalchemy.orm import sessionmaker
from sqlalchemy.exc import SQLAlchemyError
app = Flask(__name__)
app.config.from_object('config.DevelopmentConfig')
db = SQLAlchemy(app)

engine = create_engine(app.config['SQLALCHEMY_DATABASE_URI'], encoding='utf8', echo=True)


Session = sessionmaker(bind=engine)
Session.configure(bind=engine)
session = Session()


users_bundle = Blueprint("user", __name__, url_prefix="/api")


def do_the_signup(username, password):
    # return json.jsonify({'username': username, 'password': password})

    try:
        user = User(username, password)
        session.begin()
        session.add(user)
        session.commit()
        session.close()
        # using jsend standard https://labs.omniti.com/labs/jsend
        response = json.jsonify({"status": "success"})
        response.status_code = 201
        return response

    except SQLAlchemyError:
        response = json.jsonify({"status": "fail"})
        response.status_code = 400
        return response


@users_bundle.route("/user", methods=['POST'])
def signup():
    if request.method == 'POST':
        if request.content_type == 'application/json':
            username = request.json['username']
            password = request.json['password']
            # password = request.args.get('password')
            return do_the_signup(username, password)

    # else:
    #     show_the_login_form()