52 On Python 3, stdio may be None:

    53 

    54   $ hg debuguiprompt --config ui.interactive=true 0<&-

    55    abort: Bad file descriptor

    56   [255]

    57   $ hg version -q 0<&-

    58   Mercurial Distributed SCM * (glob)

    59 

    60 #if py3

    61   $ hg version -q 1>&-

    62   abort: Bad file descriptor

    63   [255]

    64 #else

    65   $ hg version -q 1>&-

    66 #endif

    67   $ hg unknown -q 1>&-

    68   hg: unknown command 'unknown'

    69   (did you mean debugknown?)

    70   [255]

    71 

    72   $ hg version -q 2>&-

    73   Mercurial Distributed SCM * (glob)

    74   $ hg unknown -q 2>&-

    75   [255]

    76