PyPy CI job fails: allmydata.test.test_sftp.Handler.test_openFile_read

[exarkun]

​https://app.circleci.com/pipelines/github/tahoe-lafs/tahoe-lafs/915/workflows/fa422fa4-5a25-46e6-8fb6-ac3df95ced0a/jobs/30087

Traceback (most recent call last):
testtools.testresult.real._StringException: Traceback (most recent call last):
  File "/tmp/tahoe-lafs.tox/pypy27/site-packages/twisted/internet/defer.py", line 654, in _runCallbacks
    current.result = callback(current.result, *args, **kw)
  File "/tmp/tahoe-lafs.tox/pypy27/site-packages/allmydata/test/test_sftp.py", line 53, in _done
    (which, expected_code, res.value.code, res))
  File "/tmp/tahoe-lafs.tox/pypy27/site-packages/allmydata/test/common_py3.py", line 125, in failUnlessReallyEqual
    self.assertEqual(a, b, msg)
  File "/tmp/tahoe-lafs.tox/pypy27/site-packages/twisted/trial/_synctest.py", line 434, in assertEqual
    super(_Assertions, self).assertEqual(first, second, msg)
  File "/opt/pypy/lib-python/2.7/unittest/case.py", line 513, in assertEqual
    assertion_func(first, second, msg=msg)
  File "/opt/pypy/lib-python/2.7/unittest/case.py", line 506, in _baseAssertEqual
    raise self.failureException(msg)
twisted.trial.unittest.FailTest: openFile unknown/file READ denied was supposed to raise SFTPError(3), not SFTPError(4): [Failure instance: Traceback: <class 'twisted.conch.ssh.filetransfer.SFTPError'>: SFTPError 4: KeyError('MURI:SSK:6vqb7ntvvz567urtssfyobry6a:hiufwra4fd2hhvzz3zeztccncknh7e6xm5tselh3c2to7xvcv6ja',)
/tmp/tahoe-lafs.tox/pypy27/site-packages/twisted/internet/base.py:913:runUntilCurrent
/tmp/tahoe-lafs.tox/pypy27/site-packages/foolscap/eventual.py:26:_turn
/tmp/tahoe-lafs.tox/pypy27/site-packages/twisted/internet/defer.py:460:callback
/tmp/tahoe-lafs.tox/pypy27/site-packages/twisted/internet/defer.py:568:_startRunCallbacks
--- <exception caught here> ---
/tmp/tahoe-lafs.tox/pypy27/site-packages/twisted/internet/defer.py:654:_runCallbacks
/tmp/tahoe-lafs.tox/pypy27/site-packages/allmydata/frontends/sftpd.py:116:_convert_error
]