Hey there, it looks like the core files have been edited in some way - potentially a mod? There is a letter or symbol that the engine is unable to process and output.
I'd recommend removing the mod in question from the directory and then doing a fresh installation of the game just to ensure the core files are restored. Even if a mod isn't present I would suggest doing this anyway as the base game shouldn't contain any letters or symbols like this.
In terms of the mod (if that does turn out to be the cause) it may be worth following this up with the creator as they may have either a new version available or a workaround.
It's possible that one of your mods or the GoG files has an unencoded value that the python script can't process.
I downloaded my stuff off Steam and use mods as well, and the classes.rpy line at 2855 shows the exact same wording and formatting. So, the error is neither in the script nor in the classes.rpy file.
My guess is that one of the files in an accessory mod has an unencodable name for one of the ryders (if you're using a language patch, that may be the primary issue; I don't use the language mods). Unfortunately, I won't be able to help much to parse through the language mods. If you have, you may want to contact the original mod thread to see if they have an update or a script fix.