How did I fix «UnsupportedBackendScheme: scheme not supported in url: s3+http://<…>» for Duplicity / Backupninja?

Other
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2

Step 1

Add the -v 9 option to the problem Duplicity command:
serverfault.com/a/1045898

Step 2

aptitude install python3-psutil

Step 3

aptitude install python3-boto3

Step 4

I changed the scheme from s3+http to boto3+s3