title: 'csrf_token': ['The CSRF token is missing.'] >> flask_wtf
body: <p>I want to make a registration form using flask_wft 
  but this line never executed </p>
  
  <pre><code>if request.method == 'POST' and form.validate():
  </code></pre>
  
  <p>because <code>form.validate()</code> return False 
  the reason is <code>csrf_token</code>.
  this is my code: </p>
  
  <pre><code>`@app.route('/', methods=['GET', 'POST'])
   def form():
       form = RegistrationForm(request.form)
       if request.method == 'POST' and form.validate():
       user = Person(f_name=form.firstName.data,
              l_name=form.lastName.data,
              email=form.email.data,city=form.city.data)
       db.session.add(user)
       db.session.commit()
       return redirect(url_for('welcome'))
   print('errors: '+ str(form.errors))
   return render_template('form.html', form=form)`
  </code></pre>
  
  <p>I got this error: <code>'csrf_token': ['The CSRF token is missing.']</code></p>
  
  <p>How to solve the problem? </p>