AttributeError: 'AnonymousUserMixin' object has no attribute 'username'

from flask import (Flask, g, render_template, flash, redirect, url_for,
                  abort)
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._get_current_object(),
                           content=form.content.data.strip())
        flash("Message posted", '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)


@login_required
@app.route('/stream')
@app.route('/stream/<username>')
def stream(username=None):
    template = 'stream.html'
    if username and username != current_user.username:
        try:
            user = models.User.select().where(
                models.User.username**username).get()
        except models.DoesNotExist:
            abort(404)
        else:
            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('/post/<int:post_id>')
def view_post(post_id):
  posts = models.Post.select().where(models.Post.id == post_id)
  if posts.count() == 0:
      abort(404)
  return render_template('stream.html', stream=posts)


@app.route('/follow/<username>')
@login_required
def follow(username):
    try:
        to_user = models.User.get(models.User.username**username)#case insensitve search **
    except models.DoesNotExist:
        abort(404)
    else:
        try:
            models.Relationship.create(
                from_user=g.user._get_current_object(),
                to_user=to_user
            )

        except models.IntegrityError:
            pass
        else:
            flash("You've followed {}!".format(to_user.username), "success")
    return redirect(url_for('stream', username=to_user.username))


@app.route('/unfollow/<username>')
@login_required
def unfollow(username):
    try:
        to_user = models.User.get(models.User.username**username)
    except models.DoesNotExist:
        abort(404)
    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)