datetime, tree, pathnames: fix test errors now that clap has the error-context feature enabled

Author: kellpossible

datetime/tests/time/mod.rs

@@ -89,5 +89,5 @@ fn parse_error_test() {
 
 #[test]
 fn command_error_test() {
-    run_test_time(&["-s", "ls", "-l"], "", "unexpected argument found", 0);
+    run_test_time(&["-s", "ls", "-l"], "", "unexpected argument '-s' found", 0);
 }

pathnames/tests/realpath/mod.rs

@@ -131,7 +131,7 @@ fn realpath_empty_path() {
     realpath_test(
         &[""],
         "",
-        "error: one of the values isn't valid for an argument\n",
+        "error: a value is required for '[PATH]...' but none was supplied\n\nFor more information, try '--help'.\n",
         2,
     );
 }

tree/tests/cp/mod.rs

@@ -440,7 +440,8 @@ fn test_cp_preserve_slink_time() {
     let dangle = &format!("{test_dir}/dangle");
     let d2 = &format!("{test_dir}/d2");
 
-    fs::create_dir(test_dir).unwrap();
+    fs::create_dir(test_dir)
+        .unwrap_or_else(|error| panic!("Error creating directory {test_dir:?}: {error:?}"));
 
     unix::fs::symlink(no_such, dangle).unwrap();