revert: 4023228 ("let's exception not bubble")

[pajod]

The report in https://github.com/benoitc/gunicorn/issues/2923 may have been not caused by a bug in Gunicorn or gevent in the first place. In any case, going from "this particular exception" to "each and every BaseException" was way excessive and is a likely explanation for https://github.com/benoitc/gunicorn/issues/3207

Context:

• https://github.com/benoitc/gunicorn/commit/40232284934c32939c0e4e78caad1987c3773e08#r144628336

Suggested changes:

• revert that patch
• reintroduce a more specific exception catching that mimics what the reverted patch tried to accomplish, while emitting a new warning.

Unfinished thoughts:

• the SSLError from wrap_socket in the eventlet worker (afaict, can only be triggered by the client sending garbage or disconnecting while Gunicorn was overloaded) cannot be dealt with this way due to class inheritance stepping outside the huge try-except block. I have a currently skipped test to reproduce this - the problem is over here: https://github.com/benoitc/gunicorn/blob/903792f152af6a27033d458020923cb2bcb11459/gunicorn/workers/geventlet.py#L153-L156

  • WIP: https://github.com/pajod/gunicorn/commit/f63030411982edf390149c8df5f10b8fdeaf8907

• Partially reverts: 40232284934c32939c0e4e78caad1987c3773e08
• Partially reverts: 0b10cbab1d6368fcab2d5a7b6fe359a6cecc81a7
• Fixes: https://github.com/benoitc/gunicorn/issues/3207

[pajod]

@benoitc Recommend you test this in conjunction with the two patches by sylt. With those, it is no longer a "simple" revert, but gets us closer to confirming the spurious tracebacks reported in #3207 are dealt with.

(hint: there is documentation on what exactly my integration tests currently encompass here: https://github.com/pajod/gunicorn/pull/3)

[benoitc]

@pajod PR must be provided over the master and don't assume that other PR may be added. There is no guarantee a separate PR will be acccepted, so PR will be enough by itself.

This PR sounds OK by itself. What could miss?

[pajod]

@benoitc This PR fits on current master. It is OK to merge by itself.