title: Adding an object via sqlalchemy throws KeyError: 'SQLALCHEMY_TRACK_MODIFICATIONS'
body: <p>This is my first python app, I have been struggling to get migrations working correctly with flask and sqlalchemy. I finally got that working but now when I run the application, I get an error when I add an object to the table that was modified with the migration code.
  This is the view the exception is thrown on db.session.add(newTag)</p>
  
  <pre><code>    def put(self):
      json_data = request.get_json(force=True)
  
      foo = json_data['foo'] if 'foo' in json_data else ''
      bar = json_data['bar'] if 'bar' in json_data else ''
      baz = json_data['baz'] if 'baz' in json_data else ''
      try:
          boo = parse(json_data['boo'])
          far = parse(json_data['far'])
      except:
          return jsonify(result='Invalid date')
  
      faz = json_data['faz'] if 'faz' in json_data else ''
  
      if faz == '':
          return jsonify(result="faz is missing")
  
      newTag = Tags(faz, baz, foo, bar, boo, far, True)
      db.session.add(newTag)
      db.session.commit()
      return {'Success, tag' + str(newTag.id) + ' created'}
  </code></pre>
  
  <p>My model looks like this</p>
  
  <pre><code>class Tags(db.Model):
  id = db.Column(db.Integer, primary_key=True)
  faz = db.Column(db.String(255))
  foo = db.Column(db.Integer)
  bar = db.Column(db.Integer)
  baz = db.Column(db.Integer)
  boo = db.Column(db.DateTime)
  far = db.Column(db.DateTime)
  status = db.Column(db.Boolean)
  
  def __init__(self, faz, foo, bar, baz, boo, far, status):
      self.faz = faz
      self.foo = foo
      self.bar = bar
      self.baz = baz
      self.boo = boo
      self.far = far
      self.status = status
  </code></pre>
  
  <p>I am not sure if any further detail is needed to assist me.
  I have put SQLALCHEMY_TRACK_MODIFICATIONS = False in the config.py file that contains my SQLALCHEMY_DATABASE_URI.</p>