Question: The build of Sphinx docs on read-the-docs fails with the following error (complete log below): 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)  Did I do something wrong or is this a bug in read-the-docs? A local build of Sphinx docs runs fine. Complete error log on read-the-docs: 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) 

Answer: The issue and the fix are described in read-the-docs issue #6554 (https://github.com/readthedocs/readthedocs.org/issues/6554): Currently all builds are failing because the automatic upgrade (since #4823 ) to pip 20.0 was buggy (see pypa/pip#7620 ). There's now a 20.0.1 release which seems to have fixed the problem for others ... but how can I force my readthedocs to also upgrade to the .1 version? The fix is to wipe out the build environment as follows (this is taken from https://docs.readthedocs.io/en/stable/guides/wipe-environment.html):  Log in to read-the-docs Go to Versions Click on the Edit button of the version you want to wipe on the right side of the page Go to the bottom of the page and click the wipe link, next to the “Save” button Now you can re-build the version with a fresh build environment!  This fix worked for me (but as of 26-Jan-2020 you have to wipe out the environment for every build -- see comment from Grimmy below).