ipykernel unconditionally calls `sys.stdout.flush()`

[twizmwazin]

ipykernel unconditionally calls sys.stdout.flush() and sys.stderr.flush(). This is a problem when either sys.stdout or sys.stderr is None, such as in pythonw.exe on windows, or Pyinstaller's windowed mode. All of these checks should be garded with a not-None check.

[gregory-shklover]

same issue here

[gregory-shklover]

Submitted PR: https://github.com/ipython/ipykernel/pull/1247