Problem with assign-labels action on PR from a forked repo

[dupuy]

Describe the problem

When a PR is created from a forked repo (rather than a branch in this repo), the assign-labels action isn't able to update the labels. This makes sense (sort of) from a security viewpoint, but isn't ideal.

At the very least, if it won't be able to update the labels, it shouldn't run this workflow.

How you can reproduce the problem

1. Create a forked repository.
2. Create a branch on that repository, and create a PR on it.
3. Check the status of the GitHub Actions workflows.

Screenshots

Context

This isn't a problem with reliabot itself, but rather with the GitHub Actions workflows.

[dupuy]

The current fix stops the error, but if it is possible, it would be better to actually assign the labels. Leaving open for further investigation.