message: Change plot version test to handle the case where gnuplot isn't installed.
diff: @@ -976,7 +976,12 @@ trait ScaleFactorTrait {
  mod test {
  #[test]
  fn version() {
  - assert_eq!(super::version().ok().map(|(major, _, _)| major >= 4),
  - Some(true));
  + if let Ok(version) = super::version() {
  + let (major, _, _) = version;
  + assert!(major >= 4);
  + }
  + else {
  + println!("Gnuplot not installed.");
  + }
  }
  }
  