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.