No results from sqlalchemy query to SQLite DB

Im attempting to validate user credentials stored in a sqlite db via sqlalchemy.

The relevant code is as follows:

from flask import Flask
from flask.ext.httpauth import HTTPBasicAuth
from models import User, Base
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker

engine = create_engine('sqlite:///users.db')
Base.metadata.bind = engine

DBSession = sessionmaker(bind=engine)
session = DBSession()

app = Flask(__name__)

auth = HTTPBasicAuth()

@auth.get_password
def get_password(username):
  return session.query(User.password).first()[0]

@app.route('/')
@auth.login_required
def welcome():
  return 'Hello, %s' %auth.username()

if __name__ == '__main__':
  app.run(host='localhost', port=8080, debug=True)

However, i get 'None' back even though there is a matching record in the DB.

When I attempt to query the DB directly from my models.py, I get the expected results. My models.py code is as follows:

from sqlalchemy import Column, Integer, String
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker

Base = declarative_base()

class User(Base):
  __tablename__ = 'userdb'
  id = Column(Integer, primary_key=True, nullable=False)
  username = Column(String(64), nullable=False)
  password = Column(String(64), nullable=False)
  email = Column(String(255), nullable=True)

engine = create_engine('sqlite:///users.db')
Base.metadata.create_all(engine)

DBSession = sessionmaker(bind=engine)
session = DBSession()

username = 'x'

match = session.query(User).filter(User.username == username).all()[0]
print match.password