Case scripts writing to stderr cause abort! :-/

[xparq]

They really shouldn't, after all. I mean, "sometimes", when my script, or tools it invokes, do as their normal business.
But, as usual: how to tell from abnormal?!...

• At least there must be a way to tell that's expected (like EXPECT_ERROR; actually, I even thought about adding an stderr arg to just that, but then I forgot.)
  -> Actually, just EXPECT_ERROR to also expect stderr to be non-empty is tempting, but I don't feel it very robust in terms of usability: I'll just keep forgetting that it's implied, and not understand why a "real" error is being ignored...