Fix config loading test

Author: matklad

tests/bad-config.rs

@@ -112,7 +112,10 @@ fn bad5() {
     assert_that(foo.cargo("new")
                    .arg("-v").arg("foo").cwd(&foo.root().join("foo")),
                 execs().with_status(101).with_stderr("\
-[ERROR] Couldn't load Cargo configuration
+[ERROR] Failed to create project `foo` at `[..]`
+
+Caused by:
+  Couldn't load Cargo configuration
 
 Caused by:
   failed to merge key `foo` between files: