Improve exception handling in get_execution_status

Previously in `get_execution_status` if a non `DbtRuntimeError` exception was
raised, the finally would be entered, but the `status`/`message` would not be
set, and thus a `status not defined` exception would get raised on attempting
to return. Tangentially, there is another issue where somehow the `node_status`
is becoming `None`. In all my playing with `get_execution_status` I found that
trying to return an undefined variable in the `finally` caused an undefined
variable exception. However, if in some python version, it instead just handed
back `None`, then this fix should also solve that.

core/dbt/task/run.py

@@ -93,11 +93,16 @@ def get_execution_status(sql: str, adapter: BaseAdapter) -> Tuple[RunStatus, str
         response, _ = adapter.execute(sql, auto_begin=False, fetch=False)
         status = RunStatus.Success
         message = response._message
+    except (KeyboardInterrupt, SystemExit):
+        raise
     except DbtRuntimeError as exc:
         status = RunStatus.Error
         message = exc.msg
-    finally:
-        return status, message
+    except Exception as exc:
+        status = RunStatus.Error
+        message = str(exc)
+
+    return (status, message)
 
 
 def track_model_run(index, num_nodes, run_model_result):