Fix checking PR body & improve error message in CD

[CasperWA]

Description:

There is a minor edge-case where the CD will fail updating the ci/dependabot-updates branch (upon a release), this minor fix sorts out that issue.
(This edge-case was found in Materials-Consortia/optimade-python-tools where similar workflows are used.)

Fixes #319.

It also adds a more informative error message for what steps to do next if the CD workflow fails in a particular step.

Type of change:

• Bug fix.
• New feature.
• Documentation update.

Checklist:

This checklist can be used as a help for the reviewer.

• Is the code easy to read and understand?
• Are comments for humans to read, not computers to disregard?
• Does a new feature has an accompanying new test (in the CI or unit testing schemes)?
• Has the documentation been updated as necessary?
• Does this close the issue?
• Is the change limited to the issue?
• Are errors handled for all outcomes?
• Does the new feature provide new restrictions on dependencies, and if so is this documented?

Comments:

[francescalb]

Is there a method to test this?

[CasperWA]

Is there a method to test this?

The way I tested it originally was locally, to see which method would work - using the gh cli to download particular PR body texts and testing different ways to format it and comparisons in order to ensure that the logic here works.
Essentially the text will be changed once someone clicks the checkboxes - and I think there are some other changes happening automatically if someone accidentally "edits" the body - even without changing anything. The latter is the edge case I suspect happened in the other repository, where the current solution didn't work. This one seems to have been working so far in the other repository :)

[francescalb]

Is there a method to test this?

The way I tested it originally was locally, to see which method would work - using the gh cli to download particular PR body texts and testing different ways to format it and comparisons in order to ensure that the logic here works. Essentially the text will be changed once someone clicks the checkboxes - and I think there are some other changes happening automatically if someone accidentally "edits" the body - even without changing anything. The latter is the edge case I suspect happened in the other repository, where the current solution didn't work. This one seems to have been working so far in the other repository :)

Thank you for the explanation. Then I think it is safe and good to go with this here as well-

[francescalb]

good