Misleading error message: java.io.IOException: The file type of ... is not supported.

In my new Bazel test rule implementation I wasn't declaring all files properly and everything worked locally. I declared a file and copied a directory containing other files into that path. Then I returned that declared file (which is a dir) as part of the `DefaultInfo`'s `runfiles` to make the content of that dir accessible to the test executable script. Some of the files in the returned dir had the `.sha256` extensions.

When this was running in CI, I was getting the following error:
`ERROR: /workdir/tests/contrib/BUILD:170:1: Couldn't build file tests/contrib/set_cmd_repro_test/test.log: failed due to unexpected I/O exception: The file type of 'bazel-out/k8-fastbuild/bin/tests/contrib/set_cmd_repro_test.test.runfiles/io_bazel_rules_docker/tests/contrib/set_cmd_repro_test_test_img_outs/set_cmd.runfiles/io_bazel_rules_docker/tests/container/set_cmd.0.config.sha256' is not supported.
java.io.IOException: The file type of 'bazel-out/k8-fastbuild/bin/tests/contrib/set_cmd_repro_test.test.runfiles/io_bazel_rules_docker/tests/contrib/set_cmd_repro_test_test_img_outs/set_cmd.runfiles/io_bazel_rules_docker/tests/container/set_cmd.0.config.sha256' is not supported.`