title: Devise error undefined method `email'
body: <p>I have tried tuning my <code>Devise</code> views and have replaced email by username. For sure, I have adjusted <code>initializers/devise.rb</code> by replacing all the occurences of <code>:email</code> by <code>:username</code>. I adjusted screens and things were working fine until I tried to delete the field <code>email</code> from database.</p>
  
  <p>After having done this, I am still able to login and create accounts as desired by using my new key (username), yet, when trying to update the user, I am getting this error message stating that email method is not defined.</p>
  
  <p>I understand that I am missing a place from where to take a call to this non-existing attribute/method but, I don't know where....</p>
  
  <p><strong>Some logs:</strong></p>
  
  <pre><code>NoMethodError in Devise::RegistrationsController#update
  undefined method `email' for #&lt;User...
  
  Rails.root: /vagrant/src/projectX
  
  Application Trace | Framework Trace | Full Trace
  activemodel (4.0.1) lib/active_model/attribute_methods.rb:439:in `method_missing'
  activerecord (4.0.1) lib/active_record/attribute_methods.rb:155:in `method_missing'
  activemodel (4.0.1) lib/active_model/validator.rb:151:in `block in validate'
  activemodel (4.0.1) lib/active_model/validator.rb:150:in `each'
  activemodel (4.0.1) lib/active_model/validator.rb:150:in `validate'
  activerecord (4.0.1) lib/active_record/validations/presence.rb:5:in `validate'
  activesupport (4.0.1) lib/active_support/callbacks.rb:283:in `_callback_before_13'
  activesupport (4.0.1) lib/active_support/callbacks.rb:377:in `_run__265703777__validate__callbacks'
  activesupport (4.0.1) lib/active_support/callbacks.rb:80:in `run_callbacks'
  </code></pre>