在阅读文档上构建Sphinx文档失败，并出现以下错误（以下完整日志）：
ImportError: cannot import name 'PackageFinder' from 'pip._internal.index' (/home/docs/checkouts/readthedocs.org/user_builds/cascade-python/envs/latest/lib/python3.7/site-packages/pip/_internal/index/__init__.py)
我做错什么了吗，或者这是文档阅读中的错误？
Sphinx文档的本地版本运行良好。
完整的文档阅读错误日志：
Read the Docs build information
Build id: 10299638
Project: cascade-python
Version: latest
Commit: a7d50bf781bd8076b10dd7024db4ccb628016c27
Date: 2020-01-21T17:03:12.876711Z
State: finished
Success: False
[rtd-command-info] start-time: 2020-01-21T17:03:13.203354Z, end-time: 2020-01-21T17:03:13.215400Z, duration: 0, exit-code: 0
git remote set-url origin https://github.com/brunorijsman/cascade-python.git
[rtd-command-info] start-time: 2020-01-21T17:03:13.276220Z, end-time: 2020-01-21T17:03:13.630658Z, duration: 0, exit-code: 0
git fetch origin --force --tags --prune --prune-tags --depth 50
From https://github.com/brunorijsman/cascade-python
2a28505..a7d50bf master -> origin/master
[rtd-command-info] start-time: 2020-01-21T17:03:13.824496Z, end-time: 2020-01-21T17:03:13.876904Z, duration: 0, exit-code: 0
git checkout --force origin/master
Previous HEAD position was 2a28505 Fix lint
HEAD is now at a7d50bf Trigger docs build
[rtd-command-info] start-time: 2020-01-21T17:03:13.941290Z, end-time: 2020-01-21T17:03:13.951085Z, duration: 0, exit-code: 0
git clean -d -f -f
[rtd-command-info] start-time: 2020-01-21T17:03:16.657644Z, end-time: 2020-01-21T17:03:22.489740Z, duration: 5, exit-code: 0
python3.7 -mvirtualenv --no-site-packages --no-download /home/docs/checkouts/readthedocs.org/user_builds/cascade-python/envs/latest
Using base prefix '/home/docs/.pyenv/versions/3.7.3'
New python executable in /home/docs/checkouts/readthedocs.org/user_builds/cascade-python/envs/latest/bin/python3.7
Not overwriting existing python script /home/docs/checkouts/readthedocs.org/user_builds/cascade-python/envs/latest/bin/python (you must use /home/docs/checkouts/readthedocs.org/user_builds/cascade-python/envs/latest/bin/python3.7)
Installing setuptools, pip, wheel...
done.
[rtd-command-info] start-time: 2020-01-21T17:03:22.562608Z, end-time: 2020-01-21T17:03:23.258281Z, duration: 0, exit-code: 1
/home/docs/checkouts/readthedocs.org/user_builds/cascade-python/envs/latest/bin/python -m pip install --upgrade --cache-dir /home/docs/checkouts/readthedocs.org/user_builds/cascade-python/.cache/pip pip
Traceback (most recent call last):
File "/home/docs/.pyenv/versions/3.7.3/lib/python3.7/runpy.py", line 193, in _run_module_as_main
"__main__", mod_spec)
File "/home/docs/.pyenv/versions/3.7.3/lib/python3.7/runpy.py", line 85, in _run_code
exec(code, run_globals)
File "/home/docs/checkouts/readthedocs.org/user_builds/cascade-python/envs/latest/lib/python3.7/site-packages/pip/__main__.py", line 16, in <module>
from pip._internal import main as _main # isort:skip # noqa
File "/home/docs/checkouts/readthedocs.org/user_builds/cascade-python/envs/latest/lib/python3.7/site-packages/pip/_internal/__init__.py", line 40, in <module>
from pip._internal.cli.autocompletion import autocomplete
File "/home/docs/checkouts/readthedocs.org/user_builds/cascade-python/envs/latest/lib/python3.7/site-packages/pip/_internal/cli/autocompletion.py", line 8, in <module>
from pip._internal.cli.main_parser import create_main_parser
File "/home/docs/checkouts/readthedocs.org/user_builds/cascade-python/envs/latest/lib/python3.7/site-packages/pip/_internal/cli/main_parser.py", line 12, in <module>
from pip._internal.commands import (
File "/home/docs/checkouts/readthedocs.org/user_builds/cascade-python/envs/latest/lib/python3.7/site-packages/pip/_internal/commands/__init__.py", line 6, in <module>
from pip._internal.commands.completion import CompletionCommand
File "/home/docs/checkouts/readthedocs.org/user_builds/cascade-python/envs/latest/lib/python3.7/site-packages/pip/_internal/commands/completion.py", line 6, in <module>
from pip._internal.cli.base_command import Command
File "/home/docs/checkouts/readthedocs.org/user_builds/cascade-python/envs/latest/lib/python3.7/site-packages/pip/_internal/cli/base_command.py", line 25, in <module>
from pip._internal.index import PackageFinder
ImportError: cannot import name 'PackageFinder' from 'pip._internal.index' (/home/docs/checkouts/readthedocs.org/user_builds/cascade-python/envs/latest/lib/python3.7/site-packages/pip/_internal/index/__init__.py)
此问题和修复在文档阅读问题＃6554（https://github.com/readthedocs/readthedocs.org/issues/6554）中进行了描述：
当前所有版本均失败，因为自动升级（自＃4823以来）到pip 20.0的过程存在问题（请参阅pypa / pip＃7620）。现在有一个20.0.1发行版似乎已经解决了其他人的问题...但是我怎么能迫使我的readthedocs也升级到.1版本？
解决方法是按如下所述清除构建环境（这是从https://docs.readthedocs.io/en/stable/guides/wipe-environment.html中获取的：]
此修复程序对我有用。