support/testing: test_which.py: use assertRunNotOk()

Use the helper to simplify the test.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

support/testing/tests/package/test_which.py

diff --git a/support/testing/tests/package/test_which.py b/support/testing/tests/package/test_which.py
index 38f528a..05ed56c 100644
--- a/support/testing/tests/package/test_which.py
+++ b/support/testing/tests/package/test_which.py
@@ -33,8 +33,7 @@
 
         # We check "which" returns an error when the program is not
         # found.
-        _, ret = self.emulator.run(f"which {alias_name}")
-        self.assertNotEqual(ret, 0)
+        self.assertRunNotOk(f"which {alias_name}")
 
         # We define a shell alias.
         alias_cmd = "/bin/true"