pwncat fails if which is not available

[fdellwing]

Bug Description

If a target has no which command (even though it is a shell built-in), pwncat fails with connection failed: no avialable pty methods

❯ python3 -m pwncat -lp 3306
[08:57:02] Welcome to pwncat 🐈!                                                                                                                                                                                              __main__.py:143
[08:57:13] received connection from 192.168.106.105:48596                                                                                                                                                                          bind.py:57
[08:57:14] 0.0.0.0:3306: normalizing shell path                                                                                                                                                                                manager.py:504
[08:57:16] 192.168.106.105:48596: registered new host w/ db                                                                                                                                                                    manager.py:504
[08:57:18] connection failed: no avialable pty methods                                                                                                                                                                         manager.py:504
(local) pwncat$

pwncat version

❯ python3 -m pwncat --version
0.4.3

Target System (aka "victim")

Arch 1.4
Box is : PG Nukem

Steps to Reproduce

1. Try to catch a reverse shell

Expected Behavior

pwncat works

I would suggest a fallback to whereis to locate a pty.

which python
/bin/bash: line 5: which: command not found
whereis python
python: /usr/bin/python3.8 /usr/bin/python /usr/bin/python3.8-config /usr/lib/python3.8 /usr/lib/python2.7 /usr/include/python3.8 /usr/share/man/man1/python.1.gz

Screenshots