sort: crash when failing to open an input file (#2265)

* sort: crash when failing to open an input file

Instead of ignoring files we fail to open, crash.
The error message does not exactly match gnu, but that would require
more effort.

* use split_whitespace instead of a manual implementation

* fix expected error on windows

* sort: update expected error message

tests/by-util/test_sort.rs

@@ -4,14 +4,14 @@ fn test_helper(file_name: &str, possible_args: &[&str]) {
     for args in possible_args {
         new_ucmd!()
             .arg(format!("{}.txt", file_name))
-            .args(&args.split(' ').collect::<Vec<&str>>())
+            .args(&args.split_whitespace().collect::<Vec<&str>>())
             .succeeds()
             .stdout_is_fixture(format!("{}.expected", file_name));
 
         new_ucmd!()
             .arg(format!("{}.txt", file_name))
             .arg("--debug")
-            .args(&args.split(' ').collect::<Vec<&str>>())
+            .args(&args.split_whitespace().collect::<Vec<&str>>())
             .succeeds()
             .stdout_is_fixture(format!("{}.expected.debug", file_name));
     }
@@ -723,3 +723,17 @@ fn test_trailing_separator() {
         .succeeds()
         .stdout_is("aax\naaa\n");
 }
+
+#[test]
+fn test_nonexistent_file() {
+    new_ucmd!()
+        .arg("nonexistent.txt")
+        .fails()
+        .status_code(2)
+        .stderr_only(
+            #[cfg(not(windows))]
+            "sort: cannot read: \"nonexistent.txt\": No such file or directory (os error 2)",
+            #[cfg(windows)]
+            "sort: cannot read: \"nonexistent.txt\": The system cannot find the file specified. (os error 2)",
+        );
+}