Improve the error message when the token has insufficient permissions about repository-dispatch

[peter-evans]

Improved the error message in the latest release.

[peter-evans]

Hi @akhmerov

Unfortunately, I don't think it's possible for the action to know exactly what the issue is. That is because the GitHub API returns 404 Not Found when the token doesn't have sufficient permissions, and when it does have sufficient permissions but the target repository URL is incorrect. I think this is by design to prevent leaking information about private repositories.

What I could do, though, is add a message which explains it could be either of the two cases I mentioned above.

[akhmerov]

It would be possible to separately detect if the bot user can find the repository but not trigger dispatch by performing another query.

However adding a message listing possible failure modes would fully address the problem, great idea!