devise: not requiring email

In my case, I removed the column email from my users in the database, and Devise started to crash. I added this:

# app/models/user.rb
def email_required?
  false
end

def email_changed?
  false
end

and it worked properly.

Please note that removing :validatable would remove password validations. So some references say you shoudn't remove it.

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Tip: Add a simple comment above those lines explaining your motives. Those after you will be thankful

Additional to removing "required" from :email column you need to remove ":validatable" from user model.

It looks like you have the email field set in the database as "not NULL" or "Allow Null" to false. And you are getting an error directly from the database. Assuming that your user model is called user you need to add the fallowing migration to fix that:

change_column :users, :email, :string, :null => true 

Documentation: http://apidock.com/rails/ActiveRecord/ConnectionAdapters/SchemaStatements/change_column