📝 Description

This PR fixes the import mlrun errors introduced from 1.11.0-rc14.
A new nuclio-jupyter version removed the boto3 (nuclio/nuclio-jupyter#194):

3. Remove boto3 from required deps - Moved to optional [boto3] extra for backward compatibility

And it revealed two bugs:

1. import mlrun boils down to import boto3 and import botocore in other imported mlrun modules.
2. The package test is faulty. This is a separate issue, to be handled in ML-11948.

This PR moved the boto3/botocore imports to the mlrun.datastore.s3 module, where they should be (and only there).
It also adds unit tests, removed unneeded imports, and moves some code the the proper module.

✅ Checklist

• I have tested the changes in this PR

🧪 Testing

I packaged mlrun locally with

make package-wheel

Created a clean Python 3.11 venv, installed the mlrun wheel in it, and ran

python -c "import mlrun"

🔗 References

• Ticket link: ML-11946

🚨 Breaking Changes?

There is a small breaking change in the error returned from S3Store.get. When the object does not exist, a FileNotFound error will be raised.