Publish to BCR app failed

[aherrmann]

Describe the bug
I've configured the publish to BCR app for rules_nixpkgs before release 0.10.0. After the release I received a failure notification from the app:

Failed to publish entry for tweag/rules_nixpkgs@v0.10.0 to the Bazel Central Registry.

An unknown error occurred. Please report an issue here: https://github.com/bazel-contrib/publish-to-bcr/issues.

I've commented on a corresponding already open issue.

Once we have an understanding of what's wrong with the configuration, we can correct the mistake.

To Reproduce
Cut a release? I'm not aware of a better way to reproduce the issue.

Expected behavior
The publish to BCR app should have created a PR to add the release to the BCR as expected.

Environment

• OS name + version: n/a
• Version of the code: 0.10.0

Additional context
none

[kormide]

There's an error in .bcr/core/source.template.json. See post in bazel-contrib/publish-to-bcr#44.