I don't think there are the line breaks, as I copied exactly the Left key definition, the following blank line and the carriage return from the original file, then I pasted it and at last I modified the line.
Well, that's odd. Just check the file out with a hex editor/viewer. It seems line endings are 0xD characters, I doubt Xep128 can write such a template config file ... In theory, Xep128 writes "native" line endings, ie in case of Windows CRLF endings (0x0D 0x0A), and just 0x0A in case of UNIX-like systems. Your file contains line ending other than either of these ... I have the suspect that your editor messed up the line endings on save, but I have no idea why. Xep128 simply uses the C89 standard fgets() function to read lines. With these non-standard line endings cause that fget treat your whole file as a single line, as it cannot identify any line endings to form more lines. Thus you have a quite long line, which causes the error message that line is too long. Even your file is shorter
still it's meaningless as it shouldn't be *one* line (or more, but with invalid line endings). Please note, that this is an operating system + operating system library (ie, Windows or Linux and their standard libraries) issue, nothing to do with Xep128 too much ... Of course I can work-around this anyway with using own line reader routines instead of the functionality of the host OS itself ... But still, it's kinda odd, how can you produce such a line endings