Sorry, I am not sure I understand. That thread only applies to older versions of drone, and is not relevant to drone 0.8. Please provide more detail including a full copy of your yaml file and the version of drone you are using.
How do you know for sure there is no special character in your yaml? I see you cat the file, however, a special character would likely be ignored or not rendered in the browser, and you would not see it. If the error message says there is an invalid character, I would assume there is an invalid character. This is something you should be able to verify, by checking character 171 after you write it.
So how would a special character end up in your secret? This would likely happen during upload, which is why we have special instructions for uploading secrets from files to preserve file content and integrity.
OK I reuploaded it and have the same error, also I’m able to use the same secrets in the GCR plugin and it works perfectly, So I would imagine the error is happening when the secret is being pulled into the file with echo.