Unexpected key error from peewee

from flask_wtf import Form
from wtforms import StringField, PasswordField
from wtforms.validators import (DataRequired, Regexp, ValidationError , Email,
                                Length, EqualTo)

from models import User

def name_exists(form, field):
    if User.select().where(User.username == field.data).exists():
        raise ValidationError('User with that name already exists.')

def email_exists(form, field):
    if User.select().where(User.email == field.data).exists():
        raise ValidationError('User with that email already exists.')

class RegisterForm(Form):
    username=StringField(
    'Username',
    validators=[
        DataRequired(),
        Regexp(
            r'^[a-zA-Z0-9_]+$',
            message="Username should be one word, letters,"
            " numbers, and underscores only."),
        name_exists])
    email = StringField(
        'Email',
        validators=[
            DataRequired(),
            Email(),
            email_exists
        ])
    password = PasswordField(
        'Password',
        validators=[
            DataRequired(),
            Length(min=2),
            EqualTo('password2', message='Passwords must match')
        ])
    password2 = PasswordField(
        'Confirm Password',
        validators=[DataRequired()])

from flask import (Flask, g, render_template, flash, redirect, url_for)
from flask.ext.login import LoginManager

import forms
import models

DEBUG = True
PORT = 8000
HOST = '0.0.0.0'

app = Flask(__name__)
app.secret_key = 'as;dklfjpoqwijfl;waj;fisjdlfijapwejifpsjadifpoij!'

login_manager = LoginManager()
login_manager.init_app(app)
login_manager.login_view = 'login'

@login_manager.user_loader
def load_user(userid):
    try:
        return models.User.get(models.User.id == userid)
    except models.DoesNotExist:
        return None

@app.before_request
def before_request():
    """Connect to database before each request"""
    g.db = models.DATABASE
    g.db.connect()

@app.after_request
def after_request(response):
    """CLose database connection after each request."""
    g.db.close()
    return response

@app.route('/register', methods=('GET', 'POST'))
def register():
    form = forms.RegisterForm()
    if form.validate_on_submit():
        flash("Yay, you registered!", "success")
        models.User.create_user(
            username=form.username.data,
            email=form.email.data,
            password=form.password.data
        )
        return redirect(url_for('index'))
    return render_template('register.html', form=form)

@app.route('/')
def index():
    return 'Hey'


if __name__ == '__main__':
    models.initialize()
    try:
        models.User.create_user(
        username='kennethlove',
        email='kenneth@teamtreehouse.com',
        password='password',
        admin=True
        )
    except ValueError:
        pass

    app.run(debug=DEBUG, host=HOST, port=PORT)

import datetime

from flask.ext.bcrypt import generate_password_hash, check_password_hash
from flask.ext.login import UserMixin
from peewee import *

DATABASE = SqliteDatabase('social.db')

class User(UserMixin, Model):
    username = CharField(unique=True)
    email = CharField(unique=True)
    password = CharField(max_length=100)
    joined_at = DateTimeField(default=datetime.datetime.now)
    is_admin = BooleanField(default=False)

    class Meta:
        database = DATABASE
        order_by = ('-joined_at')

    @classmethod
    def create_user(cls, username, email, password, admin=False):
        try:
            cls.create(
            username=username,
            email=email,
            password=generate_password_hash(password),
            is_admin=admin)
        except IntegrityError:
            raise ValueError("User already exists")

    def initialize():
        DATABASE.connect()
        DATABASE.create_tables([User], safe=True)
        DATABASE.close()