Cataloging python packages errors out if "top_level.txt" entry is missing

[wagoodman]

What happened:
As reported by Wagde Zabit

[0250] ERROR failed to catalog: 1 error occurred:
	* unable to catalog python package=/usr/local/lib/python3.8/site-packages/ptyprocess-0.6.0.dist-info/METADATA: missing python package top_level.txt (package="/usr/local/lib/python3.8/site-packages/ptyprocess-0.6.0.dist-info/METADATA"

What you expected to happen:
Cataloging should have continued to conclusion with results instead of stopping

Environment:
This was discovered with grype v0.3.0

Notes
This is where the problem is

syft/syft/cataloger/python/package_cataloger.go

Lines 125 to 127 in de2e6a1

	if topLevelRef == nil {
	return nil, nil, fmt.Errorf("missing python package top_level.txt (package=%q)", string(metadataRef.Path))
	}

, and should probably only be a log statement instead of returning an error (a best-effort strategy).

[wagde-orca]

is it fixed in grype or not yet?

[luhring]

@wagde-orca We're actually working on that right this second! We fixed one more thing in Syft, and then will update Grype to include the fix.

[luhring]

@wagde-orca Hi there, we just released grype v0.4.0 which should resolve this issue. Let us know if you have any trouble!