Replace getProcess* helpers with a single, better, API.

New submission from spiv <[email protected]>:

I think the subprocess module has the right idea: give you a single good way to start a function, and declare whether you want to capture/discard/ignore the various stdio streams etc, and then return an object with useful attributes.

So I propose that instead of `getProcessValue`, `getProcessOutput`, `getProcessOutputAndValue` (did I miss any?) we have a single method, that takes args like:

{{{
  foo(stdout=fileLikeObject, ...)
}}}

and returns a Deferred that yields an object with a `.exitValue` attribute, and perhaps others (for finding out if a signal terminated it, maybe?).  Returning an object certainly seems like a much better API than e.g. the tuples from `getProcessOutputAndValue`.  Obviously this new function would need a better name than `foo`.

Probably any new API here should try to address the problems with the existing APIs described by exarkun in a comment at http://twistedmatrix.com/trac/ticket/280.

Quite possibly the proposal in this vague sketch could be improved even further.  Please feel free to criticise, suggest improvements, suggest more precise details for the signature, etc.  I figured it was better to capture a rough idea than forget it entirely.

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Type     : enhancement
Component: core
Keywords : 
Priority : normal
Nosy     : 
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http://twistedmatrix.com/trac/ticket/3997