Redirecting pyscript with app() commands closes cmd2

[kmvanbrunt]

I have a pyscript with 1 line:
app('help')

If the script is run like: `pyscript script.py > out.txt', then cmd2 closes.

If a second line is added as shown below and the script run as before, then an exception prints before cmd2 exits.
app('help')
app('help')

Exception that prints:

Traceback (most recent call last):
File "/home/user/PycharmProjects/cmd2/cmd2/cmd2.py", line 1716, in onecmd_plus_hooks
stop = self.onecmd(statement)
File "/home/user/PycharmProjects/cmd2/cmd2/cmd2.py", line 2003, in onecmd
stop = func(statement)
File "/home/user/PycharmProjects/cmd2/cmd2/cmd2.py", line 259, in cmd_wrapper
return func(instance, args)
File "/home/user/PycharmProjects/cmd2/cmd2/cmd2.py", line 2591, in do_help
self._help_menu(args.verbose)
File "/home/user/PycharmProjects/cmd2/cmd2/cmd2.py", line 2640, in _help_menu
self.poutput("{}\n".format(str(self.doc_leader)))
File "/home/user/PycharmProjects/cmd2/cmd2/cmd2.py", line 601, in poutput
self.decolorized_write(self.stdout, msg_str)
File "/home/user/PycharmProjects/cmd2/cmd2/cmd2.py", line 579, in decolorized_write
(self.colors.lower() == constants.COLORS_TERMINAL.lower() and not fileobj.isatty()):
ValueError: I/O operation on closed file
EXCEPTION of type 'ValueError' occurred with message: 'I/O operation on closed file'

[tleonhardt]

I did a little regression testing and this bug was not present in the 0.8.9 release and is present in the 0.9.0 release. So I believe it was introduced when pyscript_bridge.py was created.

This bug isn't specific to the pyscript command, it is reproducible whenever a cmd2 command is called with py and redirected; thus the following also quits the cmd2 app:

(Cmd) py app('help') > out.txt
(py37) ✔ ~/src/cmd2/examples [master|…2]

However, running a non-cmd2 command with py does NOT exit the cmd2 app:

(Cmd) py print('hi') > out.txt
(Cmd) !cat out.txt
hi

Also, the bug only applies to file redirection and not to pipes:

(Cmd) py app('help') | grep alias
alias  help     ipy   macro  pyscript  set    shortcuts
(Cmd)

I'm not sure exactly how, but it looks like somehow sys.stdout and/or self.stdout is getting closed and then we are attempting to call the write() method on that closed file.