message: Always allow hg to be missing on CI.
diff: @@ -156,10 +156,10 @@ fn has_command(command: &str) -> bool {
  let output = match Command::new(command).arg("--version").output() {
  Ok(output) => output,
  Err(e) => {
  - // hg is not installed on GitHub macos.
  - // Consider installing it if Cargo gains more hg support, but
  - // otherwise it isn't critical.
  - if is_ci() && !(cfg!(target_os = "macos") && command == "hg") {
  + // hg is not installed on GitHub macOS or certain constrained
  + // environments like Docker. Consider installing it if Cargo gains
  + // more hg support, but otherwise it isn't critical.
  + if is_ci() && command != "hg" {
  panic!(
  "expected command `{}` to be somewhere in PATH: {}",
  command, e
  