Provide custom handler in reactor for unhandled exceptions

New submission from orestis <None>:

The current behaviour when an unhandled exception is raised is for the reactor to log it.

I cannot find any mention in the docs of how to change or suppress this behaviour, so I would like a way to provide something like this:

    def customExceptionHandler(exc):
        print 'Got an exception', exc

    reactor.setExceptionHandler(customExceptionHandler)

    assert reactor.exceptionHandler is customExceptionHandler

This would suppress the default exception handler.

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Type     : enhancement
Component: core
Keywords : 
Priority : normal
Nosy     : 
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http://twistedmatrix.com/trac/ticket/4041