DM-54302: Fall back to read the raw fits when json is not available

[hsinfang]

No description provided.

[kfindeisen]

The {e} should not be necessary if you're chaining the exception. What's the reason for catching and wrapping Exception, though?

[hsinfang]

My thought was to just add a clearer error message, but yes it's not necessary.

[kfindeisen]

Can any of this be tested in test_raw.py?

[hsinfang]

Good idea -- thank you; a test is added.

I needed to adjust the implementation to make it testable with moto. My original implementation used read_basic_metadata_from_file from astro_metadata_translator, which internally uses fsspec/s3fs with async operations. This triggers an incompatibility with moto's S3 mocking (moto has incomplete async support). I changed to a simpler implementation without fsspec and then it works with moto.