We added a circleci integration to allow running docs preview when pushing on a PR.

While for PRs coming from deepinv (i.e. non-forked) this works (see e.g. #524), this does not work from other PRs (see e.g. #575).

The error message that seems to be triggered then is:

error fetching config - config file .circleci/config.yml could not be located in gh-pages in repository deepinv/deepinv. 
Please verify that your pipeline is set up correctly (see https://circleci.com/docs/pipelines/#add-or-edit-a-pipeline)

(I say "seems" because circleci does not allow to have detailed logs on failed runs)

PS: here is the settings I've chosen in circleci