Recognize the keys of the user info dictionary provided by functions that return error objects.
Code Signing Services functions that return an error on failure may provide additional information by populating the error's user info dictionary with any of these keys. Use the
CFError function to retrieve the user info dictionary from the error object.
These keys are always supplemental and optional. Don't rely on their presence or absence to categorize an error. Use the primary OSStatus return codes listed in Code Signing Services Result Codes for that.