Improve messages.

lib/devise/models/encryptable.rb

@@ -53,7 +53,14 @@ module Devise
 
         # Returns the class for the configured encryptor.
         def encryptor_class
-          @encryptor_class ||= ::Devise::Encryptors.const_get(encryptor.to_s.classify)
+          @encryptor_class ||= case encryptor
+            when :bcrypt
+              raise "In order to use bcrypt as encryptor, simply remove :encryptable from your devise model"
+            when nil
+              raise "You need to give an :encrytor as option in order to use :encryptable"
+            else
+              ::Devise::Encryptors.const_get(encryptor.to_s.classify)
+          end
         end
 
         def password_salt

lib/devise/rails.rb

@@ -42,7 +42,8 @@ module Devise
       else
         puts "[DEVISE] You are using #{Devise.encryptor} as encryptor. From version 1.2, " <<
           "you need to explicitly add `devise :encryptable, :encryptor => :#{Devise.encryptor}` " <<
-          "to your models and comment the current value in the config/initializers/devise.rb"
+          "to your models and comment the current value in the config/initializers/devise.rb. " <<
+          "You must also add t.encryptable to your existing migrations."
       end
     end
   end