[Core] Fix aws dependency check

[Michaelvll]

Since we remove the aws dependency from the pip install skypilot, we need to check the installation of the AWS dependency in sky check.

To reproduce this:

pip install .
pip install awscli
sky check

Error:

...
  File "/home/gcpuser/skypilot/sky/clouds/service_catalog/aws_catalog.py", line 197, in validate_region_zone
    return common.validate_region_zone_impl('aws', _get_df(), region, zone)
  File "/home/gcpuser/skypilot/sky/clouds/service_catalog/aws_catalog.py", line 158, in _get_df
    _user_df = _fetch_and_apply_az_mapping(_default_df)
  File "/home/gcpuser/skypilot/sky/clouds/service_catalog/aws_catalog.py", line 114, in _fetch_and_apply_az_mapping
    user_identity_list = aws.AWS.get_current_user_identity()
  File "/home/gcpuser/skypilot/sky/clouds/aws.py", line 626, in get_current_user_identity
    except aws.botocore_exceptions().NoCredentialsError as e:
  File "/home/gcpuser/skypilot/sky/adaptors/aws.py", line 88, in wrapper
    raise ImportError('Fail to import dependencies for AWS. '
ImportError: Fail to import dependencies for AWS. Try pip install "skypilot[aws]"

Tested (run the relevant ones):

• Code formatting: bash format.sh
• Any manual or new tests for this PR (please specify below)
  • The reproducible code above.
• All smoke tests: pytest tests/test_smoke.py
• Relevant individual smoke tests: pytest tests/test_smoke.py::test_fill_in_the_name
• Backward compatibility tests: bash tests/backward_comaptibility_tests.sh

[concretevitamin]

Thanks @Michaelvll.

Can we also check #2926 ? E.g., when [aws] or [gcp] are not installed, does sky show-gpus work (it should)?

[Michaelvll]

Thanks @Michaelvll.

Can we also check #2926 ? E.g., when [aws] or [gcp] are not installed, does sky show-gpus work (it should)?

Thanks for mentioning this! Just tried sky show-gpus in a clean env with docker run -it --rm --name skypilot-debug2 berkeleyskypilot/skypilot-debug /bin/bash, and it seems working normally without [aws] or [gcp].