silence_gevent.py

# allow to silence error reporting for certain 'expected exceptions'

# gevent prints a error report including a traceback for each failed
# greenlet. this is at times useful, but you're currently forced to
# either handle exceptions in those greenlets or live with the traceback
# on stderr.

# patch_gevent introduces a class variable 'expected_exceptions' to
# gevent's greenlet class. This is a tuple of exceptions for which no
# error report should be printed to stderr.

# This can be set in a custom greenlet subclass, or even at runtime like
# in:

# ,----
# | from gevent import spawn, getcurrent
# |
# | def divide():
# |     getcurrent().expected_exceptions += (ZeroDivisionError,)
# |     1/0
# |
# | spawn(divide).join()
# `----

from gevent import hub, greenlet


def handle_error(self, context, type, value, tb):
    expected_exceptions = getattr(context, "expected_exceptions", self.NOT_ERROR)
    if not issubclass(type, expected_exceptions):
        self.print_exception(context, type, value, tb)
    if context is None or issubclass(type, self.SYSTEM_ERROR):
        self.handle_system_error(type, value)


def patch_gevent():
    greenlet.Greenlet.expected_exceptions = hub.Hub.NOT_ERROR
    hub.Hub.handle_error = handle_error