Fix random test failure
Fix random test failure

While working on reproducible builds for openSUSE, I noticed
that test_popen_nice would randomly fail on 1-core-VMs

         remotenice = gw.remote_exec(getnice).receive()
         gw.exit()
         if remotenice is not None:
             gw = makegateway("popen//nice=5")
             remotenice2 = gw.remote_exec(getnice).receive()
 >           assert remotenice2 == remotenice + 5
 E           assert 0 == (0 + 5)

alfredodeza/execnet,pytest-dev/execnet