Bubble errors even if pipeline isn't used (#2080)

tests/shell/pipeline/commands/external.rs

@@ -10,6 +10,16 @@ fn shows_error_for_command_not_found() {
     assert!(actual.err.contains("Command not found"));
 }
 
+#[test]
+fn shows_error_for_command_not_found_in_pipeline() {
+    let actual = nu!(
+        cwd: ".",
+        "ferris_is_not_here.exe | echo done"
+    );
+
+    assert!(actual.err.contains("Command not found"));
+}
+
 #[test]
 fn automatically_change_directory() {
     use nu_test_support::playground::Playground;