Misleading Error Message If Requested File Does Not Exist

This is a wonderful tool and has successfully recovered many broken Audacity Projects.

If the target .aup3 file is misspelled or otherwise does not exist, the message:

"unable to open database file"

appears which is technically correct, but unfortunately in this specific instance it is also quite worrying. Perhaps a message

"specified database file does not exist"

might be more appropriate.

For additional insight, see: https://forum.audacityteam.org/viewtopic.php?p=445707#p445707