Comment 11 for bug 1868363

Version 3.20-5ubuntu2-ppa1 is what I have installed.

I don't even think it directly calls the interpreter: I discovered that my hashbang was
#!/bin/bash
while the complained was about /usr/bin/dash (and still is).

That rather sounds like system rather than exec is being used here. Or the system shell is sandwiched in between in some other manner. I seem to remember that for potential interpreter scripts there once was something called "sanitized_helper" that worked in rules.

Sorry not to be able to be more specific: this whole underdocumented mess and framework is just beyond me.