nixosTests.systemd: modify test to use new error output from systemd 257

Changed files
+1 -1
nixos
tests
+1 -1
nixos/tests/systemd.nix
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# it's not possible because we're not in a tty when grepping
# (i.e. hacky way to ensure that the error from above doesn't appear here).
_, out = machine.execute("systemctl --user edit testservice2.service 2>&1")
-
assert out.rstrip("\n") == "Cannot edit units if not on a tty."
+
assert out.rstrip("\n") == "Cannot edit units interactively if not on a tty."
# Regression test for https://github.com/NixOS/nixpkgs/issues/105049
with subtest("systemd reads timezone database in /etc/zoneinfo"):