[Buildroot] Issue with capture of emulator output in runtime test infra

[Edgar Bonet]

Hello!

Thomas Petazzoni wrote about support/testing/infra/emulator.py:
> the command [...] gets wrapped on two lines, like this:
>
> # curl -s -o /dev/null -w "%{http_code}\n" -X POST -H "Content-Type: application
> /json" -d '{"email": "test", "name": "test"}' http://127.0.0.1:5000

Is it just a coincidence that the line got wrapped at exactly
80 columns, or is it always at this width? 80 columns is the width of a
traditional IBM punched card, a VT100 terminal, and likely the default
for a pseudo-terminal. Does the behavior change if the width of the
pseudo-terminal ("dimensions" attribute of spawn()) is changed?

Regards,

Edgar.