I uploaded my export.pkl file to Google Drive and updated all the requisite libraries to match with the render requirements.txt and was still receiving the error:
_pickle.UnpicklingError: invalid load key, '<'.
After running the docker image locally I finally found the problem was because my .pkl file was over 25Mb. Google Drive prompts large download attempts with a warning page about virus scanning (even using that confirmation link as the download url fails!). The html warning page is downloaded instead
<!DOCTYPE html><html><head><title>Google Drive - Virus scan warning</title>
...
</html>
hence the invalid key <!
My solution was to upload to Dropbox where I didn’t have any problems…
If you must use Google Drive, use the Drive API:
https://developers.google.com/drive/api/v3/manage-downloads