Rollup merge of #161415 - cdcp2:fix-path-expect-messages, r=nia-e

Update expect messages in path docs to better follow guidelines

Updates the `.expect()` messages in `library/std/src/path.rs`
to better follow the guidance for `expect` messages.

Related to #159751.

Author: jhpratt

library/std/src/path.rs

@@ -3329,7 +3329,7 @@ impl Path {
     /// use std::path::Path;
     ///
     /// let path = Path::new("/Minas/tirith");
-    /// let metadata = path.metadata().expect("metadata call failed");
+    /// let metadata = path.metadata().expect("the path should point to an existing file or directory");
     /// println!("{:?}", metadata.file_type());
     /// ```
     #[stable(feature = "path_ext", since = "1.5.0")]
@@ -3348,7 +3348,7 @@ impl Path {
     /// use std::path::Path;
     ///
     /// let path = Path::new("/Minas/tirith");
-    /// let metadata = path.symlink_metadata().expect("symlink_metadata call failed");
+    /// let metadata = path.symlink_metadata().expect("the path should exist");
     /// println!("{:?}", metadata.file_type());
     /// ```
     #[stable(feature = "path_ext", since = "1.5.0")]
@@ -3483,7 +3483,7 @@ impl Path {
     /// use std::path::Path;
     ///
     /// let path = Path::new("/laputa/sky_castle.rs");
-    /// let path_link = path.read_link().expect("read_link call failed");
+    /// let path_link = path.read_link().expect("the path should be an existing symbolic link");
     /// ```
     #[stable(feature = "path_ext", since = "1.5.0")]
     #[inline]
@@ -3504,7 +3504,7 @@ impl Path {
     /// use std::path::Path;
     ///
     /// let path = Path::new("/laputa");
-    /// for entry in path.read_dir().expect("read_dir call failed") {
+    /// for entry in path.read_dir().expect("the path should point to an existing directory") {
     ///     if let Ok(entry) = entry {
     ///         println!("{:?}", entry.path());
     ///     }
@@ -3569,7 +3569,7 @@ impl Path {
     ///
     /// ```no_run
     /// use std::path::Path;
-    /// assert!(!Path::new("does_not_exist.txt").try_exists().expect("Can't check existence of file does_not_exist.txt"));
+    /// assert!(!Path::new("does_not_exist.txt").try_exists().expect("the path's existence should be verifiable"));
     /// assert!(Path::new("/root/secret_file.txt").try_exists().is_err());
     /// ```
     ///