我维护了一个开源库xarray，它使用 pytest 在 Travis-CI 上运行集成测试。我们使用堆栈 conda 安装科学 Python。
今天早些时候，我们的五个测试版本中有两个（Python 3.5 和 3.6，但不是 Python 2.7 或 3.4）开始无缘无故地失败。pytest 本身失败了，带有一个神秘的引用：
$ py.test xarray --cov=xarray --cov-config ci/.coveragerc --cov-report term-missing --verbose $EXTRA_FLAGS
Traceback (most recent call last):
File "/home/travis/miniconda/envs/test_env/bin/py.test", line 6, in <module>
sys.exit(py.test.main())
File "/home/travis/miniconda/envs/test_env/lib/python3.6/site-packages/_pytest/config.py", line 49, in main
config = _prepareconfig(args, plugins)
File "/home/travis/miniconda/envs/test_env/lib/python3.6/site-packages/_pytest/config.py", line 168, in _prepareconfig
pluginmanager=pluginmanager, args=args)
File "/home/travis/miniconda/envs/test_env/lib/python3.6/site-packages/_pytest/vendored_packages/pluggy.py", line 745, in __call__
return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
File "/home/travis/miniconda/envs/test_env/lib/python3.6/site-packages/_pytest/vendored_packages/pluggy.py", line 339, in _hookexec
return self._inner_hookexec(hook, methods, kwargs)
File "/home/travis/miniconda/envs/test_env/lib/python3.6/site-packages/_pytest/vendored_packages/pluggy.py", line 334, in <lambda>
_MultiCall(methods, kwargs, hook.spec_opts).execute()
File "/home/travis/miniconda/envs/test_env/lib/python3.6/site-packages/_pytest/vendored_packages/pluggy.py", line 613, in execute
return _wrapped_call(hook_impl.function(*args), self.execute)
File "/home/travis/miniconda/envs/test_env/lib/python3.6/site-packages/_pytest/vendored_packages/pluggy.py", line 250, in _wrapped_call
wrap_controller.send(call_outcome)
File "/home/travis/miniconda/envs/test_env/lib/python3.6/site-packages/_pytest/helpconfig.py", line 68, in pytest_cmdline_parse
config = outcome.get_result()
File "/home/travis/miniconda/envs/test_env/lib/python3.6/site-packages/_pytest/vendored_packages/pluggy.py", line 279, in get_result
raise ex[1].with_traceback(ex[2])
File "/home/travis/miniconda/envs/test_env/lib/python3.6/site-packages/_pytest/vendored_packages/pluggy.py", line 265, in __init__
self.result = func()
File "/home/travis/miniconda/envs/test_env/lib/python3.6/site-packages/_pytest/vendored_packages/pluggy.py", line 614, in execute
res = hook_impl.function(*args)
File "/home/travis/miniconda/envs/test_env/lib/python3.6/site-packages/_pytest/config.py", line 957, in pytest_cmdline_parse
self.parse(args)
File "/home/travis/miniconda/envs/test_env/lib/python3.6/site-packages/_pytest/config.py", line 1121, in parse
self._preparse(args, addopts=addopts)
File "/home/travis/miniconda/envs/test_env/lib/python3.6/site-packages/_pytest/config.py", line 1084, in _preparse
self.pluginmanager.load_setuptools_entrypoints('pytest11')
File "/home/travis/miniconda/envs/test_env/lib/python3.6/site-packages/_pytest/vendored_packages/pluggy.py", line 510, in load_setuptools_entrypoints
plugin = ep.load()
File "/home/travis/miniconda/envs/test_env/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2409, in load
return self.resolve()
File "/home/travis/miniconda/envs/test_env/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2415, in resolve
module = __import__(self.module_name, fromlist=['__name__'], level=0)
ModuleNotFoundError: No module named 'hypothesis.extra.pytestplugin'
关于这件事，有几件事让我感到惊讶：
- 我们不使用假设或安装
hypothesis.extra.pytestplugin。我不知道这是从哪里来的。 - 没有什么明显的变化会触发此错误。它首先出现在一行 doc change之后。安装的 Python 库，包括 conda 安装的特定二进制构建，似乎完全相同。（不过，如果您愿意，您可以
diff自己构建输出。）
如果您对发生的事情有任何线索或猜测，我们将不胜感激！我什至不知道在堆栈中的哪个位置提交错误。