Error warning for failed list upload

[thetmtech]

It would be nice if there was an error page or popup if a list import fails. Currently, it sits for a long time on "Uploading" then either flashes "Upload Successful" or "Upload Failed" and then returns to the main filter lists page.

If you're not watching it you miss the message.

[dkwiebe]

@tysonkcv Is this still relevant with the recent changes we made?