fix: gazelle panics when "# gazelle:ignore" doesn't have a value

[stdll00]

PR Checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature (please, look at the "Scope of the project" section in the README.md file)
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

What is the current behavior?

If # gazelle:ignore line exists gazelle panics.

commit hash 6434e34 (added new test line)
//gazelle:gazelle_test failes

exec ${PAGER:-/usr/bin/less} "$0" || exit 1
Executing tests from //gazelle:gazelle_test
-----------------------------------------------------------------------------
--- FAIL: TestGazelleBinary (12.00s)
    --- FAIL: TestGazelleBinary/ignored_invalid_imported_module (0.38s)
        python_test.go:188: expected gazelle exit code: 0
            got: 2
        python_test.go:188: expected gazelle stderr: 
            got: panic: runtime error: index out of range [1] with length 1
            
            goroutine 1 [running]:
            github.com/bazelbuild/rules_python/gazelle.(*comment).asAnnotation(0x1004293c0?)
            	gazelle/parser.go:207 +0x13c
            github.com/bazelbuild/rules_python/gazelle.annotationsFromComments({0x14000031040, 0x4, 0x1f8?})
            	gazelle/parser.go:230 +0xac
            github.com/bazelbuild/rules_python/gazelle.(*python3Parser).parse(0x140001c6338, 0x14000010130)
            	gazelle/parser.go:131 +0x5a4
            github.com/bazelbuild/rules_python/gazelle.(*Python).GenerateRules(0x0?, {0x14000142370, {0x1400007a690, 0x6f}, {0x0, 0x0}, 0x140001a26e0, {0x0, 0x0, 0x0}, ...})
            	gazelle/generate.go:197 +0x68c
            main.runFixUpdate.func1({0x1400007a690, 0x6f}, {0x0, 0x0}, 0x14000142370, 0x0?, 0x140001a26e0, {0x0, 0x0, 0x0}, ...)
            	external/bazel_gazelle/cmd/gazelle/fix-update.go:298 +0xc88
            github.com/bazelbuild/bazel-gazelle/walk.Walk.func1(0x14000142370, {0x1400007a690, 0x6f}, {0x0, 0x0}, 0x0)
            	external/bazel_gazelle/walk/walk.go:179 +0x3ec
            github.com/bazelbuild/bazel-gazelle/walk.Walk(0x14000142370, {0x1400007e730?, 0x5, 0x5}, {0x140000694f0, 0x1, 0x1}, 0x0, 0x1400015f588)
            	external/bazel_gazelle/walk/walk.go:182 +0x190
            main.runFixUpdate({0x1400001e084, 0x6f}, 0x16fd42c0c?, {0x14000012050, 0x1, 0x1})
            	external/bazel_gazelle/cmd/gazelle/fix-update.go:275 +0x580
            main.run({0x1400001e084?, 0x6f?}, {0x14000012050?, 0x1?, 0x1?})
            	external/bazel_gazelle/cmd/gazelle/gazelle.go:95 +0x230
            main.main()
            	external/bazel_gazelle/cmd/gazelle/gazelle.go:72 +0xe4
            
        python_test.go:142: "" exists
        python_test.go:142: "/ignored_invalid_imported_module" exists
        python_test.go:142: "/ignored_invalid_imported_module/BUILD" exists
        python_test.go:142: "/ignored_invalid_imported_module/README.md" exists
        python_test.go:142: "/ignored_invalid_imported_module/WORKSPACE" exists
        python_test.go:142: "/ignored_invalid_imported_module/__init__.py" exists
        python_test.go:142: "/ignored_invalid_imported_module/gazelle_python.yaml" exists
        python_test.go:142: "/ignored_invalid_imported_module/test.yaml" exists
FAIL

What is the new behavior?

Ignores erorr. This is similar behavior if module name is invalid.

Does this PR introduce a breaking change?

• Yes
• No

Other information

[f0rmiga]

This API is invalid. The # gazelle:ignore on a Python file requires a value. If you want to replace the panic with a more specific error, then you will have to change asAnnotation to also return an error.

[stdll00]

Thank you for review. Fixed to return the error.

[f0rmiga]

Looks good! Thanks for adding the test. Just check the suggestions before merging.