Merge pull request #1573 from railsaholic/use_existing_find_by_username_or_email

Utilize already existing method 'find_by_username_or_email'

spec/models/user_spec.rb

@@ -829,8 +829,8 @@ describe User do
 
     context 'when multiple users are found' do
       it 'raises an exception' do
-        user_query = stub(to_a: [stub, stub])
-        User.stubs(:where).with(username_lower: 'bob').returns(user_query)
+        user_query = [stub, stub]
+        User.stubs(:find_by_username).with('bob').returns(user_query)
 
         expect { User.find_by_username_or_email('bob') }.to raise_error(Discourse::TooManyMatches)
       end