bundle2: don't try to recover from a GeneratorExit (issue4785)
GeneratorExit means the other end of the conversation has already
stopped listening, so don't try and yield out error
information. Instead, just let the GeneratorExit propagate normally.
This should resolve esoteric issues observed with servers that have
aggressive timeouts waiting for data to send to clients logging
internal Python errors[0]. This has been observed with both gunicorn's
gevent worker model and with scm-manager's built-in webserver (which
itself is something sitting inside jetty.)
0: Exception RuntimeError: 'generator ignored GeneratorExit' in <generator object getchunks at 0x7fd2f6c586e0> ignored
(binary:application/octet-stream)