plumbum hides stderr of pipes

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>>> from plumbum.cmd import cat, head
>>> from plumbum import FG
>>> cat['/dev/urndom'] & FG(1)
/bin/cat: /dev/urndom: No such file or directory
>>> (cat['/dev/urndom'] | head['-c', '10']) & FG(retcode=1)
>>>

I would expect to see the standard error output of cat printed to the stderr of the Python process. For instance, zsh shows this:

❯❯❯ /bin/cat /dev/urndom | head -c10
/bin/cat: /dev/urndom: No such file or directory

[woky]

I don’t want to capture stderr. It should be printed to actual sys.stderr and not discarded. If you do in e.g. Bash

foo=$(ls /12345 || echo foo)

you get stdout into $foo but stderr will still be printed to shell’s stderr. Plumbum seems to discard it for no reason.

[hashbrowncipher]

@woky I looked up the docstring for __call__, and found that it says “A shortcut for run(args), returning only the process’ stdout”. I was able to get output going to sys.stderr by doing:

>>> bash['ls /123456 || true'] & FG

If instead capturing stderr is preferred, one can do:

>>> bash.run('ls /123456 || true')
(0, '', "ls: cannot access '/123456': No such file or directory\n")