can not import name routes in a Flask app

I tried to test my Flask application following this blog but I said:

(venv) mike@mike-Inspiron-3543:~/Documents/programming/microblog$ flask shell
Usage: flask shell [OPTIONS]

Error: While importing "microblog", an ImportError was raised:

Traceback (most recent call last):
  File "/home/mike/Documents/programming/microblog/venv/local/lib/python2.7/site-packages/flask/cli.py", line 235, in locate_app
    __import__(module_name)
  File "/home/mike/Documents/programming/microblog/microblog.py", line 1, in <module>
    from app import app, db
  File "/home/mike/Documents/programming/microblog/app/__init__.py", line 6, in <module>
    from app import routes, models
  File "/home/mike/Documents/programming/microblog/app/app.py", line 6, in <module>
ImportError: cannot import name routes

The database was represented in the application by with an instance in app/__init__.py :

from flask import Flask
from config import Config
from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate

from app import routes, models

from flask_login import LoginManager

app = Flask(__name__)
app.config.from_object(Config)
db = SQLAlchemy(app)
migrate = Migrate(app, db)

login = LoginManager(app)

login.login_view = 'login'

I have a file app/routes.py :

from flask import render_template, flash, redirect
from app.forms import LoginForm
from app import app

from flask_login import current_user, login_user
from app.models import User

from flask_login import logout_user

from flask import request
from werkzeug.urls import url_parse


@app.route('/')
@app.route('/index')
@login_required
def index():
    user = {'username': 'Miguel'}
    posts = [
        {
            'author': {'username': 'John'},
            'body': 'Beautiful day in Portland!'
        },
        {
            'author': {'username': 'Susan'},
            'body': 'The Avengers movie was so cool!'
        }
    ]
    return render_template("index.html", title='Home Page', posts=posts)

@app.route('/login', methods=['GET', 'POST'])
def login():
    if current_user.is_authenticated:
        return redirect(url_for('index'))
    form = LoginForm()
    if form.validate_on_submit():
        user = User.query.filter_by(username=form.username.data).first()
        if user is None or not user.check_password(form.password.data):
            flash('Invalid username or password')
            return redirect(url_for('login'))
        login_user(user, remember=form.remember_me.data)
        next_page = request.args.get('next')
        if not next_page or url_parse(next_page).netloc != '':
            next_page = url_for('index')
        return redirect(next_page)
    return render_template('login.html', title='Sign In', form=form)

@app.route('/logout')
def logout():
    logout_user()
    return redirect(url_for('index'))

from flask_login import login_required