Tor integration tests fail because Chutney needs Python 3

[sajith]

​Chutney is going to need Python 3, ​going forward.

Currently invoking chutney modules directly from Tahoe fails, because Tahoe uses Python 2, and Chutney now requires Python 3.

[sajith]

Error log, for the record:

2020-07-20T15:18:46.2736540Z _________________ ERROR at setup of test_onion_service_storage _________________
2020-07-20T15:18:46.2736840Z 
2020-07-20T15:18:46.2738660Z reactor = <twisted.internet.selectreactor.SelectReactor object at 0x104e0b990>
2020-07-20T15:18:46.2740100Z temp_dir = '/var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/tahoe_6R88E'
2020-07-20T15:18:46.2740720Z chutney = '/var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/tahoe_6R88E/chutney'
2020-07-20T15:18:46.2741260Z request = <SubRequest 'tor_network' for <Function test_onion_service_storage>>
2020-07-20T15:18:46.2741390Z 
2020-07-20T15:18:46.2741900Z     @pytest.fixture(scope='session')
2020-07-20T15:18:46.2742140Z     def tor_network(reactor, temp_dir, chutney, request):
2020-07-20T15:18:46.2742340Z         # this is the actual "chutney" script at the root of a chutney checkout
2020-07-20T15:18:46.2742510Z         chutney_dir = chutney
2020-07-20T15:18:46.2743400Z         chut = join(chutney_dir, 'chutney')
2020-07-20T15:18:46.2743610Z     
2020-07-20T15:18:46.2744130Z         # now, as per Chutney's README, we have to create the network
2020-07-20T15:18:46.2744350Z         # ./chutney configure networks/basic
2020-07-20T15:18:46.2744510Z         # ./chutney start networks/basic
2020-07-20T15:18:46.2744760Z     
2020-07-20T15:18:46.2745200Z         env = environ.copy()
2020-07-20T15:18:46.2745820Z         env.update({"PYTHONPATH": join(chutney_dir, "lib")})
2020-07-20T15:18:46.2746020Z         proto = _DumpOutputProtocol(None)
2020-07-20T15:18:46.2746190Z         reactor.spawnProcess(
2020-07-20T15:18:46.2746330Z             proto,
2020-07-20T15:18:46.2746650Z             sys.executable,
2020-07-20T15:18:46.2746910Z             (
2020-07-20T15:18:46.2747740Z                 sys.executable, '-m', 'chutney.TorNet', 'configure',
2020-07-20T15:18:46.2748320Z                 join(chutney_dir, 'networks', 'basic'),
2020-07-20T15:18:46.2748490Z             ),
2020-07-20T15:18:46.2748740Z             path=join(chutney_dir),
2020-07-20T15:18:46.2748850Z             env=env,
2020-07-20T15:18:46.2749020Z         )
2020-07-20T15:18:46.2749330Z >       pytest_twisted.blockon(proto.done)
2020-07-20T15:18:46.2749520Z 
2020-07-20T15:18:46.2750100Z integration/conftest.py:413: 
2020-07-20T15:18:46.2751460Z _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
2020-07-20T15:18:46.2752380Z .tox/integration/lib/python2.7/site-packages/pytest_twisted.py:74: in blockon
2020-07-20T15:18:46.2752930Z     return blockon_default(d)
2020-07-20T15:18:46.2753040Z _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
2020-07-20T15:18:46.2753650Z 
2020-07-20T15:18:46.2754510Z d = <Deferred at 0x106f64820 current result: <twisted.python.failure.Failure twisted.internet.error.ProcessTerminated: A process has ended with a probable error condition: process ended with exit code 1.>>
2020-07-20T15:18:46.2754690Z 
2020-07-20T15:18:46.2754800Z     def blockon_default(d):
2020-07-20T15:18:46.2755100Z         current = greenlet.getcurrent()
2020-07-20T15:18:46.2755460Z         assert (
2020-07-20T15:18:46.2756090Z             current is not _instances.gr_twisted
2020-07-20T15:18:46.2756420Z         ), "blockon cannot be called from the twisted greenlet"
2020-07-20T15:18:46.2756610Z         result = []
2020-07-20T15:18:46.2756710Z     
2020-07-20T15:18:46.2756990Z         def cb(r):
2020-07-20T15:18:46.2757380Z             result.append(r)
2020-07-20T15:18:46.2758060Z             if greenlet.getcurrent() is not current:
2020-07-20T15:18:46.2758390Z                 current.switch(result)
2020-07-20T15:18:46.2758870Z     
2020-07-20T15:18:46.2759190Z         d.addCallbacks(cb, cb)
2020-07-20T15:18:46.2759450Z         if not result:
2020-07-20T15:18:46.2759900Z             _result = _instances.gr_twisted.switch()
2020-07-20T15:18:46.2760570Z             assert _result is result, "illegal switch in blockon"
2020-07-20T15:18:46.2760830Z     
2020-07-20T15:18:46.2761260Z         if isinstance(result[0], failure.Failure):
2020-07-20T15:18:46.2761770Z >           result[0].raiseException()
2020-07-20T15:18:46.2762880Z E           ProcessTerminated: A process has ended with a probable error condition: process ended with exit code 1.
2020-07-20T15:18:46.2763030Z 
2020-07-20T15:18:46.2763840Z .tox/integration/lib/python2.7/site-packages/pytest_twisted.py:95: ProcessTerminated
2020-07-20T15:18:46.2764850Z ---------------------------- Captured stdout setup -----------------------------
2020-07-20T15:18:46.2765610Z Cloning into '/var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/tahoe_6R88E/chutney'...
2020-07-20T15:18:46.2765810Z Traceback (most recent call last):
2020-07-20T15:18:46.2767290Z   File "/Users/runner/hostedtoolcache/Python/2.7.18/x64/lib/python2.7/runpy.py", line 163, in _run_module_as_main
2020-07-20T15:18:46.2767610Z     mod_name, _Error)
2020-07-20T15:18:46.2767920Z   File "/Users/runner/hostedtoolcache/Python/2.7.18/x64/lib/python2.7/runpy.py", line 119, in _get_module_details
2020-07-20T15:18:46.2784250Z     code = loader.get_code(mod_name)
2020-07-20T15:18:46.2784500Z   File "/Users/runner/hostedtoolcache/Python/2.7.18/x64/lib/python2.7/pkgutil.py", line 281, in get_code
2020-07-20T15:18:46.2785220Z     self.code = compile(source, self.filename, 'exec')
2020-07-20T15:18:46.2785550Z   File "/private/var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/tahoe_6R88E/chutney/lib/chutney/TorNet.py", line 103
2020-07-20T15:18:46.2785720Z     def mkdir_p(*d, mode=448):
2020-07-20T15:18:46.2785870Z                        ^
2020-07-20T15:18:46.2786000Z SyntaxError: invalid syntax