set error to the field specified in unlock_keys config

closes #2418

lib/devise/models/lockable.rb

@@ -146,16 +146,16 @@ module Devise
           if access_locked?
             yield
           else
-            self.errors.add(:email, :not_locked)
+            self.errors.add(Devise.unlock_keys.first, :not_locked)
             false
           end
         end
 
       module ClassMethods
-        # Attempt to find a user by its email. If a record is found, send new
+        # Attempt to find a user by its unlock keys. If a record is found, send new
         # unlock instructions to it. If not user is found, returns a new user
         # with an email not found error.
-        # Options must contain the user email
+        # Options must contain the user's unlock keys
         def send_unlock_instructions(attributes={})
           lockable = find_or_initialize_with_errors(unlock_keys, attributes, :not_found)
           lockable.resend_unlock_token if lockable.persisted?

test/models/lockable_test.rb

@@ -185,12 +185,12 @@ class LockableTest < ActiveSupport::TestCase
   end
 
   test 'should require all unlock_keys' do
-      swap Devise, :unlock_keys => [:username, :email] do
-          user = create_user
-          unlock_user = User.send_unlock_instructions(:email => user.email)
-          assert_not unlock_user.persisted?
-          assert_equal "can't be blank", unlock_user.errors[:username].join
-      end
+    swap Devise, :unlock_keys => [:username, :email] do
+      user = create_user
+      unlock_user = User.send_unlock_instructions(:email => user.email)
+      assert_not unlock_user.persisted?
+      assert_equal "can't be blank", unlock_user.errors[:username].join
+    end
   end
 
   test 'should not be able to send instructions if the user is not locked' do
@@ -200,6 +200,15 @@ class LockableTest < ActiveSupport::TestCase
     assert_equal 'was not locked', user.errors[:email].join
   end
 
+  test 'should not be able to send instructions if the user if not locked and have username as unlock key' do
+    swap Devise, :unlock_keys => [:username] do
+      user = create_user
+      assert_not user.resend_unlock_token
+      assert_not user.access_locked?
+      assert_equal 'was not locked', user.errors[:username].join
+    end
+  end
+
   test 'should unlock account if lock has expired and increase attempts on failure' do
     swap Devise, :unlock_in => 1.minute do
       user = create_user