readline - why does does it only do carriage return and not a line feed when reaching end of line?

I developped a python application that uses the cmd module to make an interactive command-line interface. This cmd module uses readline for command-line management: completion, history...

My issue is: on the computer I'm trying to use that app, when I type too long lines, it goes back to the beginning of the line and doesn't put a line feed. So I'm writing over the line itself. This makes browsing and editing commands in history a real pain. Although it works well on my development box.

I tried changing the shell from which I started python (from bash to sh), no difference, I tried to change the terminal I used (from Terminator to XTerm or UXTerm), no difference.

What would be your guess about where it comes from and how to solve this issue?