Errors in the delayed response makes debugging hard

[miyagawa]

Run this code with Twiggy, and your browser gets 400 Bad Response where developers have no idea what was actually causing errors.

my $app = sub {
    my $env = shift;
    return sub {
        my $respond = shift;
        die "Blah";
    };
};

Imagine there's a typo or any other runtime errors in between. The error messages should be useful for debugging, but the current behavior is that the error is caught by Twiggy server and thrown away. At least it should make it a 500 response instead of 400 and print the error to psgi.errors.

[bbrtj]

Almost 10 years later I encounter this issue while writing websocket code for Twiggy. Any chance of fixing this?