message: Use [/] instead of hardcoded / so that it's portable on Windows.
diff: @@ -1509,7 +1509,7 @@ fn doc_workspace_open_different_library_and_package_names() {
  execs()
  .with_status(0)
  .with_stderr_contains("[..] Documenting foo v0.1.0 ([..])")
  - .with_stderr_contains("[..] Opening [..]/foo/target/doc/foolib/index.html")
  + .with_stderr_contains("[..] Opening [..][/]foo[/]target[/]doc[/]foolib[/]index.html")
  );
  }
  