Please describe the problem.

Originally blamed datalad but apparently git annex add --json does not include error message in the json output. In our case it was due to permission issues.

$ git annex add more --json
  more: setFileMode: permission denied (Operation not permitted)
git-annex: add: 1 failed

If you use --json-error-messages it does work, at least in this permissions error case. So nothing more needs to be done. --Joey