stdio.StandardIO breaks, readhack code in process.py to blame

[gtalvola]

stdio.StandardIO under some conditions will erroneously detect a closed connection, preventing any further output to stdout. It has to do with the "readhack" code in process.py. I've attached a couple of scripts that should make the problem clear. Just run teststdout and notice that the two runs of stdout.py produce different output. Then, edit stdout.py to uncomment out the s._writer.enableReadHack = False line, and re-run it, and this time the output should agree.

I discovered the problem using Twisted 2.4.0, but the relevant parts of process.py look the same in the trunk, so I expect the problem is still there.

[gtalvola]

BTW, I'm using Python 2.4.1 on Fedora Core 3 with a 2.6.16.20 kernel, in case that matters.

[therve]

I think this a duplicate of #2259.