chore: switch to bzl_library that checks docs

[alexeagle]

workaround bazelbuild/bazel-skylib#568

[aspect-workflows]

Test

⚠️ Buildkite build #476 failed.

//py:defs.doc_extract failed to build

in deps attribute of starlark_doc_extract rule //py:defs.doc_extract: missing bzl_library targets for
Starlark module(s) //py/private/py_venv:defs.bzl. Since this rule was created by the macro 'bzl_library', the
error might have been caused by the macro implementation

//docs:py_test failed to build

stardoc failed: error executing Stardoc command (from target //docs:py_test) bazel-out/k8-opt-exec-ST-a828a81199fe/bin/external/io_bazel_stardoc/stardoc/stardoc '--input=@//py:defs.bzl' '--workspace_name=aspect_rules_py' '--symbols=py_test' '--symbols=py_test_rule' ... (remaining 4 arguments skipped)
 
Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
 
com.google.devtools.build.skydoc.SkydocMain$StarlarkEvaluationException: File py/defs.bzl imported '//py/private/py_venv:defs.bzl', yet py/private/py_venv/defs.bzl was not found, even at roots [., external/aspect_rules_py].
	at com.google.devtools.build.skydoc.SkydocMain.recursiveEval(SkydocMain.java:444)
	at com.google.devtools.build.skydoc.SkydocMain.eval(SkydocMain.java:292)
	at com.google.devtools.build.skydoc.SkydocMain.main(SkydocMain.java:159)
Caused by: java.nio.file.NoSuchFileException: py/private/py_venv/defs.bzl
	at com.google.devtools.build.skydoc.SkydocMain.getInputSource(SkydocMain.java:494)
	at com.google.devtools.build.skydoc.SkydocMain.recursiveEval(SkydocMain.java:424)
	at com.google.devtools.build.skydoc.SkydocMain.recursiveEval(SkydocMain.java:440)
	... 2 more
Stardoc documentation generation failed: File py/defs.bzl imported '//py/private/py_venv:defs.bzl', yet py/private/py_venv/defs.bzl was not found, even at roots [., external/aspect_rules_py].

//docs:py_binary failed to build

stardoc failed: error executing Stardoc command (from target //docs:py_binary) bazel-out/k8-opt-exec-ST-a828a81199fe/bin/external/io_bazel_stardoc/stardoc/stardoc '--input=@//py:defs.bzl' '--workspace_name=aspect_rules_py' '--symbols=py_binary' '--symbols=py_binary_rule' ... (remaining 3 arguments skipped)
 
Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
 
com.google.devtools.build.skydoc.SkydocMain$StarlarkEvaluationException: File py/defs.bzl imported '//py/private/py_venv:defs.bzl', yet py/private/py_venv/defs.bzl was not found, even at roots [., external/aspect_rules_py].
	at com.google.devtools.build.skydoc.SkydocMain.recursiveEval(SkydocMain.java:444)
	at com.google.devtools.build.skydoc.SkydocMain.eval(SkydocMain.java:292)
	at com.google.devtools.build.skydoc.SkydocMain.main(SkydocMain.java:159)
Caused by: java.nio.file.NoSuchFileException: py/private/py_venv/defs.bzl
	at com.google.devtools.build.skydoc.SkydocMain.getInputSource(SkydocMain.java:494)
	at com.google.devtools.build.skydoc.SkydocMain.recursiveEval(SkydocMain.java:424)
	at com.google.devtools.build.skydoc.SkydocMain.recursiveEval(SkydocMain.java:440)
	... 2 more
Stardoc documentation generation failed: File py/defs.bzl imported '//py/private/py_venv:defs.bzl', yet py/private/py_venv/defs.bzl was not found, even at roots [., external/aspect_rules_py].

💡 To reproduce the build failures, run

bazel build //py:defs.doc_extract //docs:py_test //docs:py_binary