use the helper

integration/conftest.py

@@ -541,15 +541,13 @@ def tor_network(reactor, temp_dir, chutney, request):
     })
     chutney_argv = (sys.executable, '-m', 'chutney.TorNet')
     def chutney(argv):
-        proto = _DumpOutputProtocol(None)
-        reactor.spawnProcess(
-            proto,
+        return dump_output(
+            reactor,
             sys.executable,
             chutney_argv + argv,
             path=join(chutney_root),
             env=env,
         )
-        return proto.done
 
     # now, as per Chutney's README, we have to create the network
     pytest_twisted.blockon(chutney(("configure", basic_network)))