Stop writing a 500 on top of a response that already started

[gyanu2507]

Worker timeout fires SIGABRT → sys.exit(1). That's a BaseException, so the except Exception guard that checks headers_sent never ran. handle_error then wrote a 500 onto the same socket, which is how wget ended up with ISE HTML concatenated onto a partial download.

Once headers are out we just close, same as a regular exception.

Fixes #3410

[benoitc]

Thanks for tracking this down, the fix is right: once headers are out we should close, not write a 500.

One thing on the catch itself: except BaseException is too broad. The abort handler does sys.exit(1), so the only thing reaching here beyond a normal Exception is SystemExit. Could you narrow it to:

except (Exception, SystemExit):

in all three workers possibly.

[benoitc]

lPlease look at my comment about the exception. Once handled , the code is OK to merge.

[gyanu2507]

Narrowed the headers-sent catch in sync, gthread, and the async worker to except (Exception, SystemExit).

[benoitc]

Thanks @gyanu2507, merged.