Refactor _doReadOrWrite implementations to remove duplication

New submission from exarkun <[email protected]>:

`twisted/internet/pollreactor.py`, `twisted/internet/epollreactor.py`, and `twisted/internet/gtk2reactor.py` all contain `_doReadOrWrite` implementations which bear a striking resemblance to each other.

It would be nice if these poll-like reactors could all share one implementation of this logic.

One thing to note is that `gtk2reactor` behaves subtly differently from the others with respect to half-close.  If a selectable is both readable and writeable simultaneously, `pollreactor` and `epollreactor` will treat write errors as completely closing the connection.  `gtk2reactor`, on the other hand, appears as though it will treat this case as a half-close.  The latter behavior seems wrong and should probably be eliminated by the refactoring.  Adding a test for it might also be nice.


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Type     : task
Component: core
Keywords : 
Priority : normal
Nosy     : 
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http://twistedmatrix.com/trac/ticket/4357