read repo_name when opening repos

src/repo/profile/mod.rs

@@ -2,7 +2,8 @@
 //! ```rust
 //! use gentoo_utils::repo::Repo;
 //!
-//! let repo = Repo::new("/var/db/repos/gentoo");
+//! let repo = Repo::new("/var/db/repos/gentoo")
+//!     .expect("failed to open repo");
 //! let profile = repo.evaluate_profile("default/linux/23.0")
 //!     .expect("failed to evaluate profile");
 //!