I just added a Pegasus 2 to my MACbook and tried to run promiseutil in applescript, and it won't run even in the editor. So I wrote a bash script (which runs fine) and ran it from applescript, I get an error for a non-zero exit code, so I added an 'exit 0' to the script and now it runs but there is no output.
At this point, my best guess is that this is a library path issue, as applescript does not carry the shell enviornment along with it, if promiseutil has some additional libraries, they cannot be seen in appletalk. But I'm not having much luck tracing system calls with dtruss for some reason.
I developed a workaround wherein I send the promiseutil command to macOS Terminal, where it executes fine. It's not an elegant solution, although it's effective, which bugs me.
I think this by itself proves that it's an enviornmental issue, when you send it to terminal, you get the full shell enviornment.
So the applescript solution will require adding the missing enviornment to the promiseutil call, but High Sierra shows nothing for $LD_LIBRARY_PATH or $DYLD_LIBRARY_PATH, I'm going to have to do some more research on this, they've hidden a lot of stuff.
But a simpler approach might be to use cron to run the shellscript. But this may run into the same problem as cron jobs also lack an enviornment, and we don't know what enviornment promiseutil needs in order to run.
I will keep looking into it time allowing.