Flask Principal Login

#run.py
from overwatch import app
app.run()

#__init__.py
from flask import Flask, session, g, render_template, request, redirect, url_for, Response
import websiteconfig as config
from flaskext.principal import Identity, Principal, RoleNeed, UserNeed, \
            Permission, identity_changed, identity_loaded

app = Flask(__name__)
app.debug = config.DEBUG
app.secret_key = config.SECRET_KEY


principals = Principal(app)
principals._init_app(app)


#error handling
@app.errorhandler(404)
def not_found(error):
    return render_template('404.html'), 404

@app.errorhandler(403)
def page_not_found(e):
    session['redirected_from'] = request.url
    return redirect(url_for('crud.login'))

# handle login failed
@app.errorhandler(401)
def page_not_found(e):
    return Response('<p>Login failed</p>')

from overwatch.views import general
from overwatch.views import crud


app.register_blueprint(general.mod)
app.register_blueprint(crud.mod)

#general.py
from flask import Blueprint, render_template, session, redirect, url_for, \
     request, flash, g, Response, jsonify
from flaskext.principal import Identity, Principal, RoleNeed, UserNeed, \
            Permission, identity_changed, identity_loaded
from .. import principals

mod = Blueprint('general', __name__)

normal_role = RoleNeed('normal')
normal_permission = Permission(normal_role)

@mod.route('/')
@normal_permission.require(http_exception=403)
def index():
    return "YOU'RE IN"


#crud.py
from flask import Blueprint, render_template, session, redirect, url_for, \
     request, flash, g, Response, jsonify, abort, Response
from mongokit import Connection, Document
from db import user_exists, email_exists, return_attribute, check_credentials
from forms import RegistrationForm, LoginForm
from .. import app
from flaskext.principal import Identity, Principal, RoleNeed, UserNeed, \
            Permission, identity_changed, identity_loaded
from general import normal_role, normal_permission

mod = Blueprint('crud', __name__)

@mod.route('/login/', methods=['GET', 'POST'])
def login():
    form = LoginForm(request.form)
    error = None
    if request.method == 'POST' and form.validate():
        if check_credentials(form.username.data,form.password.data):
            identity = Identity(form.username.data)
            identity_changed.send(app, identity=identity)
            return redirect(session['redirected_from'])
        else:
            return abort(401)
    return render_template('login.html', form=form, error=error)

@app.route("/logout/")
def logout():
    for key in ['identity.name', 'identity.auth_type', 'redirected_from']:
        try:
            del session[key]
        except:
            pass
    return Response('<p>Logged out</p>')

@identity_loaded.connect_via(app)
def on_identity_loaded(sender, identity):
    identity.provides.add(normal_role)