cmdserver: protect pipe server streams against corruption caused by direct io Because pipe-mode server uses stdio as IPC channel, other modules should not touch stdio directly and use ui instead. However, this strategy is brittle because several Python functions read and write stdio implicitly. print 'hello' # should use ui.write() # => ch = 'h', size = 1701604463 'ello', data = '\n' This patch adds protection for such mistakes. Both stdio files and low-level file descriptors are redirected to /dev/null while command server uses them.