export PUDB_TTY=... not working

[ElBartel]

Diverting the debugger interface to a diffent tty by setting the PUDB_TTY environment variable does not work.

Simply try:
touch any-script.py; PUDB_TTY=$(tty) python -mpudb any-script.py

This results in a ValueError: I/O operation on closed file. exception.

This is due to calling tty_file.close() in _get_debugger() introduced in Close tty file when dne querying terminal info)
The prolblem is not present, when this call does not happen.

[inducer]

Probably fixed by #656. Let me know if that's not the case.