Using https://api.backblazeb2.com output to stderr causing problems for automation that only expects errors and warnings on stderr

[globau]

#941 makes the very reasonable change so the Using https://api.backblazeb2.com won't interfere with JSON output; redirecting this string from stdout to stderr.

However, the fallout of this change is automation that only expects errors and warnings to be output to stderr would now report this message, in my case generating unnecessary reports of warnings. Reporting on stderr has been valuable in the past to ensure deprecation warnings are exposed, as well as any other non-fatal issue.

If you were using the logging framewok I'd propose changing the Using https://api.backblazeb2.com message to DEBUG level, however as you only have the two options and given it doesn't belong in either location perhaps the message should be dropped?