[2017-03-30 17:04:11 +0000] [1] [INFO] Starting gunicorn 19.7.1
 [2017-03-30 17:04:11 +0000] [1] [INFO] Listening at: http://0.0.0.0:80 (1)
 [2017-03-30 17:04:11 +0000] [1] [INFO] Using worker: sync
 [2017-03-30 17:04:11 +0000] [9] [INFO] Booting worker with pid: 9
 [2017-03-30 17:04:37,572] ERROR in app: Exception on /register [POST]
 Traceback (most recent call last):
   File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1982, in wsgi_app
     response = self.full_dispatch_request()
   File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1614, in full_dispatch_request
     rv = self.handle_user_exception(e)
   File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1517, in handle_user_exception
     reraise(exc_type, exc_value, tb)
   File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1612, in full_dispatch_request
     rv = self.dispatch_request()
   File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1598, in dispatch_request
     return self.view_functions[rule.endpoint](**req.view_args)
   File "/deploy/project/__init__.py", line 16, in register
     models.db.session.add(user)
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/scoping.py", line 157, in do
     return getattr(self.registry(), name)(*args, **kwargs)
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/util/_collections.py", line 990, in __call__
     return self.registry.setdefault(key, self.createfunc())
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/session.py", line 2829, in __call__
     return self.class_(**local_kw)
   File "/usr/local/lib/python2.7/dist-packages/flask_sqlalchemy/__init__.py", line 144, in __init__
     track_modifications = app.config['SQLALCHEMY_TRACK_MODIFICATIONS']
 KeyError: 'SQLALCHEMY_TRACK_MODIFICATIONS'

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_login import LoginManager, login_user , logout_user , current_user , login_required
import datetime

app = Flask(__name__)

app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////tmp/test.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
db = SQLAlchemy(app)
login_manager = LoginManager()
login_manager.init_app(app)
login_manager.login_view = 'login'

@login_manager.user_loader
def load_user(id):
    return User.query.get(int(id))

class User(db.Model):
    __tablename__ = "users"
    id = db.Column('user_id',db.Integer , primary_key=True)
    username = db.Column('username', db.String(20), unique=True , index=True)
    password = db.Column('password' , db.String(10))
    email = db.Column('email',db.String(50),unique=True , index=True)
    registered_on = db.Column('registered_on' , db.DateTime)

    def __init__(self , username ,password , email):
        self.username = username
        self.password = password
        self.email = email
        self.registered_on = datetime.datetime.utcnow()

    def is_authenticated(self):
        return True

    def is_active(self):
        return True

    def is_anonymous(self):
        return False

    def get_id(self):
        return unicode(self.id)

    def __repr__(self):
        return '<User %r>' % (self.username)

from flask import Flask, Response

app = Flask(__name__)

from flask import Flask
from flask import render_template
from functools import wraps
from flask import request, Response, redirect, url_for, request, session, abort
import models

@app.route('/register' , methods=['GET','POST'])
def register():
    if request.method == 'GET':
        return render_template('register.html')
    user = models.User(request.form['username'] , request.form['password'],request.form['email'])
    models.db.session.add(user)
    models.db.session.commit()
    flash('User successfully registered')
    return redirect(url_for('login'))

@app.route('/login',methods=['GET','POST'])
def login():
    if request.method == 'GET':
        return render_template('login.html')
    username = request.form['username']
    password = request.form['password']
    registered_user = models.User.query.filter_by(username=username,password=password).first()
    if registered_user is None:
        flash('Username or Password is invalid' , 'error')
        return redirect(url_for('login'))
    login_user(registered_user)
    flash('Logged in successfully')
    return redirect(request.args.get('next') or url_for('index'))