twisted.internet.test.test_internet should test for interleaving of delayed calls and I/O processing

New submission from danderson <None>:

A reactor should be designed so as to correctly interleave calls to reactor.callLater(0,...) and IO events. Otherwise, a callback recursively callLater(0)-ing itself could DoS the reactor by preventing it from ever doing any I/O.

There are currently no tests which verify this functionality, although thankfully current reactors are designed with this issue in mind. There should be one, in `twisted.internet.test.test_internet`, so that it gets exercised on all reactor implementations.

How it should look exactly is not yet exactly known, but it should be event-driven, and demonstrate that callLater(0) callbacks and I/O events are interleaved.

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Type     : enhancement
Component: core
Keywords : 
Priority : normal
Nosy     : 
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http://twistedmatrix.com/trac/ticket/4026