//src/test/shell/bazel:starlark_repository_test is not compatible with Python 3

### Description of the bug:

https://storage.googleapis.com/bazel-untrusted-buildkite-artifacts/01861769-00f9-409f-9fb0-561d0415f679/src/test/shell/bazel/starlark_repository_test/shard_4_of_6/test_attempts/attempt_1.log: `TypeError: can't concat str to bytes`

### What's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

_No response_

### Which operating system are you running Bazel on?

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### What is the output of `bazel info release`?

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### If `bazel info release` returns `development version` or `(@non-git)`, tell us how you built Bazel.

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### What's the output of `git remote get-url origin; git rev-parse master; git rev-parse HEAD` ?

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### Have you found anything relevant by searching the web?

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### Any other information, logs, or outputs that you want to share?

_No response_

Start with //src/test/shell/bazel:starlark_repository_test and inspect the linked shard log for the TypeError: can't concat str to bytes failure. Run the test with Python 3, identify the incompatible string/bytes handling, and verify that the target passes without the reported error.

Written by the indexing model from the issue text.