Gracefully handle not being able to find a project

[punkstar]

Steps to Reproduce

• magedbm2 get projectthatdoesntexist

Expected Outcome

An error saying 'projectthatdoesntexist' does not exist.

Actual Outcome

Failed to download the backup file: Error executing "GetObject" on "https://yourbucketname.s3.eu-west-2.amazonaws.com/projectthatdoesntexist/"; AWS HTTP error: Unable to open /tmp/ using mode w+: fopen(/tmp/): failed to open stream: Is a directory