v2.2.2: Fix handling of no-op matrix conversions

[stephane-caron]

This patch version fixes handling of no-op conversions in test sets (dense to dense or sparse to sparse).

Added

• Expose exceptions from top-level module

Fixed

• Bump Python version to actual requirement of 3.9 or above
• Handle no-op conversion from dense to dense properly
• Handle no-op conversion from sparse to sparse properly

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This discussion was created from the release v2.2.2.