I received this error message:
specify either the --profile flag or --access-key-id with --secret-access-key and optionally --session-token, but not both
My configuration had the --profile flag set and AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, and AWS_SESSION_TOKEN environment variables set. I was in the process of refactoring things so was between using env vars and using the profile (i.e. generating a profile using those env vars, and then setting the --profile flag).
I found this error initially confusing because I never set the --access-key-id, etc. flags, but it seems they are being inferred from the env vars. Perhaps updating the error message would be enough? I could probably PR that if it is wanted.