refactor(test): split assertions

Split an assertion on a conjunction into multiple assertions, to make it
easier to see which of the individual checks failed.

Suggested-by: Babis Chalios <[email protected]>
Signed-off-by: Patrick Roy <[email protected]>

Author: roypat

tests/framework/microvm.py

@@ -337,14 +337,16 @@ def kill(self):
                 f"ps ax -o pid,cmd -ww | grep {self.jailer.jailer_id}"
             )
 
+            assert not stderr, f"error querying processes using `ps`: {stderr}"
+
             offenders = []
             for proc in stdout.splitlines():
                 _, cmd = proc.lower().split(maxsplit=1)
                 if "firecracker" in proc and not cmd.startswith("screen"):
                     offenders.append(proc)
 
             # make sure firecracker was killed
-            assert not stderr and not offenders, (
+            assert not offenders, (
                 f"Firecracker reported its pid {self.firecracker_pid}, which was killed, but there still exist processes using the supposedly dead Firecracker's jailer_id: \n"
                 + "\n".join(offenders)
             )