👌 IMPROVE: CTRL-C on running process (#4771)

Do not call `kill` on a process that is already being killed.
Also log a different message,
so that the user can see that the original CTRL-C was actioned.

aiida/engine/runners.py

@@ -235,6 +235,9 @@ def _run(self, process: TYPE_RUN_PROCESS, *args: Any, **inputs: Any) -> Tuple[Di
 
             def kill_process(_num, _frame):
                 """Send the kill signal to the process in the current scope."""
+                if process_inited.is_killing:
+                    LOGGER.warning('runner received interrupt, process %s already being killed', process_inited.pid)
+                    return
                 LOGGER.critical('runner received interrupt, killing process %s', process_inited.pid)
                 process_inited.kill(msg='Process was killed because the runner received an interrupt')