Watcher doesn't work with FreeBSD

[jkazimierczak]

Due diligence
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Describe the bug
Responder doesn't respond to prompts, despite matching regex.

To Reproduce
Steps to reproduce the behaviour (please attach a minimal example):

1. Create the script on the remote host and make it executable:

#!/bin/bash

read -s -p "Password: " password
echo -n

echo $password

I placed it in the user's home directory and named it "prompt.sh".

2. Execute following fabric code:

from invoke import Responder
from fabric import Connection


user = ""
passwd = ""
host = ""

ssh = Connection(f"{user}@{host}", connect_kwargs={"password": passwd})
passwd_watcher = Responder(pattern=r"Password.*", response="somePassWD40")

ssh.run(
    "./prompt.sh",
    # encoding="utf-8",
    # echo=False,
    pty=True,
    watchers=[passwd_watcher],
)

Expected behaviour
Prompt is supplied with the response automatically and .run() invocation finishes successfully.

Environment
Make sure your report gets the attention it deserves: bug reports with missing
information may be ignored or punted back to you, delaying a fix. The below
constitutes a bare minimum; more info is almost always better:

Python 3.10
Client-side OS: Windows 10, 22H2 (19045.3324)  |  OpenSSH 8.1.0.1
Server-side OS: FreeBSD 13.2-RELEASE
Fabric version: 3.2.2

Also tried with these fabric versions: 3.1.0, 2.5.0, 2.6.0, 2.7.1, but the result is the same - response is not being handled correctly.

Additional context
Manually providing the response for prompts also causes .run() to "hang in place". I tried also providing the response with and without watchers specified.