Is your feature request related to a problem? Please describe.
When a merged PR could not be scanned it is difficult to figure out why.
Describe the solution you'd like
Ideally instead of just returning sha and commit message it would be nice to also get a more detailed explanation of why it could not be parsed.
I see this as on debug logging (core.debug) option in https://github.com/googleapis/release-please-action, like here

Describe alternatives you've considered
Add error message to logger:

    } catch (err) {
      logger.debug(
        `commit could not be parsed: ${commit.sha} ${
          commit.message.split('\n')[0]
        } - ${(err as Error).message}`