Better error message when no referrer is set by the browser

[Philipp Wolfer]

I just tried to post a comment on a bug page and received the attached error message. The problem was, that I use RefControl to block the referrer, but LP will require a referrer when posting comments.

While the solution for me was simple I nearly missed it, since the error message is confusing. At first I did not see the relevant text ("No REFERER Header Launchpad requires a REFERER header to perform this action"), which is somewhat hidden inside the message.

I suggest to show only the message itself and hide the backtrace by default.

[Deryck Hodge (deryck)]

This is due to a general problem with error reporting for lazr-js widgets, especially when commenting.