cannot import name 'PackageFinder' errors won't go away

[nomicode]

• Read the Docs project URL: https://readthedocs.org/projects/crate/
• Build URL (if applicable): https://readthedocs.org/projects/crate/builds/10348432/
• Read the Docs username (if applicable):

builds failing with:

ImportError: cannot import name 'PackageFinder' from 'pip._internal.index' (/home/docs/checkouts/readthedocs.org/user_builds/crate/envs/4.1/lib/python3.7/site-packages/pip/_internal/index/__init__.py)

I have seen other issue reports (e.g., #6554) that suggest the build issues we're having can be fixed by wiping the build environment

I have tried that multiple times. and indeed, sometimes the build works again afterward. but new commits to the branch end up failing with this error again

if you go to https://readthedocs.org/projects/crate/builds/ you will see a string of builds all triggered automatically today. some of them passing, and some of them failing with this error

I have not manually triggered any builds today. and I have not wiped any of the build environments. this is all just activity from GitHub hooks

[stsewd]

Hi, sorry about that. Yesterday we found the problem #6598, the fix well be released soon.

[stsewd]

Fix was deployed

[nomicode]

thank you! <3