Fix muted exceptions in fm_dispatch due to self SIGKILL

This commit fixes the issue where fm_dispatch would call SIGKILL on itself before reraising the exception that caused it to fail.

src/_ert/forward_model_runner/fm_dispatch.py

@@ -144,11 +144,6 @@ def _stop_reporters(
             reporter.stop(exited_event=exited_event)
 
 
-def sigterm_handler(_signo, _stack_frame):
-    signal.signal(signal.SIGTERM, signal.SIG_DFL)
-    os.kill(0, signal.SIGTERM)
-
-
 def fm_dispatch(args):
     parser = argparse.ArgumentParser(
         description=(
@@ -207,13 +202,14 @@ def sigterm_handler(_signo, _stack_frame):
 
 def main():
     os.nice(19)
-    signal.signal(signal.SIGTERM, sigterm_handler)
     try:
         fm_dispatch(sys.argv)
-    except Exception as e:
+    except Exception as exc:
+        print(f"fm_dispatch failed with {exc=}")
         pgid = os.getpgid(os.getpid())
-        os.killpg(pgid, signal.SIGTERM)
-        raise e
+        os.killpg(
+            pgid, signal.SIGTERM
+        )  # This will trigger the sigterm_handler, which shuts down the reporters and SIGKILLS any remaining processes.
 
 
 if __name__ == "__main__":

tests/ert/unit_tests/forward_model_runner/test_fm_dispatch.py

@@ -484,3 +484,20 @@ async def wait_for_msg(msg_type):
             event_from_json(zmq_server.messages[-1]).error_msg
             == FORWARD_MODEL_TERMINATED_MSG
         )
+
+
+async def test_fm_dispatch_main_signals_sigterm_on_exception(capsys):
+    def mock_fm_dispatch_raises(*args):
+        raise RuntimeError("forward model critical error")
+
+    with (
+        patch("_ert.forward_model_runner.fm_dispatch.os.killpg") as mock_killpg,
+        patch("_ert.forward_model_runner.fm_dispatch.os.getpgid") as mock_getpgid,
+        patch("_ert.forward_model_runner.fm_dispatch.fm_dispatch") as mock_fm_dispatch,
+    ):
+        mock_getpgid.return_value = 17
+        mock_fm_dispatch.side_effect = mock_fm_dispatch_raises
+        _ert.forward_model_runner.fm_dispatch.main()
+    assert "forward model critical error" in capsys.readouterr().out
+
+    mock_killpg.assert_called_with(17, signal.SIGTERM)