UnboundLocalError: local variable 'to_user' referenced before assignment

from flask import (Flask, g, render_template, flash, redirect, url_for)
from flask.ext.bcrypt import check_password_hash
from flask.ext.login import (LoginManager, login_user, logout_user,
                             login_required, current_user)

import forms
import models

DEBUG = True
PORT = 8000
HOST = '0.0.0.0'

app = Flask(__name__)
app.secret_key = 'auoesh.bouoastuh.43,uoausoehuosth3ououea.auoub!'

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 the database before each request."""
    g.db = models.DATABASE
    g.db.connect()
    g.user = current_user


@app.after_request
def after_request(response):
    """Close the 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('/login', methods=('GET', 'POST'))
def login():
    form = forms.LoginForm()
    if form.validate_on_submit():
        try:
            user = models.User.get(models.User.email == form.email.data)
        except models.DoesNotExist:
            flash("Your email or password doesn't match!", "error")
        else:
            if check_password_hash(user.password, form.password.data):
                login_user(user)
                flash("You've been logged in!", "success")
                return redirect(url_for('index'))
            else:
                flash("Your email or password doesn't match!", "error")
    return render_template('login.html', form=form)


@app.route('/logout')
@login_required
def logout():
    logout_user()
    flash("You've been logged out! Come back soon!", "success")
    return redirect(url_for('index'))


@app.route('/new_post', methods=('GET', 'POST'))
@login_required
def post():
    form = forms.PostForm()
    if form.validate_on_submit():
        models.Post.create(user=g.user.id,
                           content=form.content.data.strip())
        flash("Message posted! Thanks!", "success")
        return redirect(url_for('index'))
    return render_template('post.html', form=form)


@app.route('/')
def index():
    stream = models.Post.select().limit(100)
    return render_template('stream.html', stream=stream)


@app.route('/stream')
@app.route('/stream/<username>')
def stream(username=None):
    template = 'stream.html'
    if username and username != current_user.username:
        user = models.User.select().where(models.User.username**username).get()
        stream = user.posts.limit(100)
    else:
        stream = current_user.get_stream().limit(100)
        user = current_user
    if username:
        template = 'user_stream.html'
    return render_template(template, stream=stream, user=user)

@app.route('/follow/<username>')
@login_required
def follow(username):
    try:
        to_user = models.User.get(models.User.username*username)
    except models.DoesNotExist:
        pass
    else:
        try:
            models.Relationship.create(
                from_user=g.user._get_current_object(),
                to_user=to_user
            )
        except models.IntegrityError:
            pass
        else:
            flash("Youre now following {}!".format(to_user.username), "success")
    return redirect(url_for('stream', username=to_user.username))

@app.route('/unfollow/<username>')
@login_required
def un_follow(username):
    try:
        to_user = models.User.get(models.User.username*username)
    except models.DoesNotExist:
        pass
    else:
        try:
            models.Relationship.get(
                from_user=g.user._get_current_object(),
                to_user=to_user
            ).delete_instance()
        except models.IntegrityError:
            pass
        else:
            flash("You've unfollowed {}!".format(to_user.username), "success")
    return redirect(url_for('stream', username=to_user.username))

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)

from flask_wtf import Form
from wtforms import StringField, PasswordField, TextAreaField
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()]
    )


class LoginForm(Form):
    email = StringField('Email', validators=[DataRequired(), Email()])
    password = PasswordField('Password', validators=[DataRequired()])


class PostForm(Form):
    content = TextAreaField("What's up?", validators=[DataRequired()])

import datetime

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

DATABASE = SqliteDatabase('social.db', threadlocals=True)

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',)

    def get_posts(self):
        return Post.select().where(Post.user == self)

    def get_stream(self):
        return Post.select().where(
            (Post.user == self)
        )

    def following(self):
        """The users that we are following."""
        return (
            User.select().join(
                Relationship, on=Relationship.to_user
            ).where(
                Relationship.from_user == self
            )
        )

    def followers(self):
        """Get users following the current user"""
        return (
            User.select().join(
                Relationship, on=Relationship.from_user
            ).where(
                Relationship.to_user == self
            )
        )

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


class Post(Model):
    timestamp = DateTimeField(default=datetime.datetime.now)
    user = ForeignKeyField(
        rel_model=User,
        related_name='posts'
    )
    content = TextField()

    class Meta:
        database = DATABASE
        order_by = ('-timestamp',)


class Relationship(Model):
    from_user = ForeignKeyField(User, related_name='relationships')
    to_user = ForeignKeyField(User, related_name='related_to')

    class Meta:
        database = DATABASE
        indexes = (
            (('from_user', 'to_user'), True),
        )


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