Use path-spec instead of path for module-not-found errors

The path portion of the path-spec is often not enough to debug
what wasn't found. This change includes the entire path-spec
when giving an error for e.g. `use NotFound;`

src/core/CompUnit/Repository.pm6

@@ -28,7 +28,7 @@ role CompUnit::Repository {
         self.next-repo
           ?? self.next-repo.load($file)
           !! nqp::die("Could not find $file in:\n"
-              ~ $*REPO.repo-chain.map(*.Str).join("\n").indent(4));
+              ~ $*REPO.repo-chain.map(*.path-spec).join("\n").indent(4));
     }
 
     # Returns the CompUnit objects describing all of the compilation

src/core/CompUnit/Repository/AbsolutePath.pm6

@@ -32,7 +32,7 @@ class CompUnit::Repository::AbsolutePath does CompUnit::Repository {
         }
 
         return self.next-repo.load($file) if self.next-repo;
-        die("Could not find $file in:\n" ~ $*REPO.repo-chain.map(*.Str).join("\n").indent(4));
+        die("Could not find $file in:\n" ~ $*REPO.repo-chain.map(*.path-spec).join("\n").indent(4));
     }
 
     method loaded(--> Iterable:D) {

src/core/Exception.pm6

@@ -3029,7 +3029,7 @@ my class X::CompUnit::UnsatisfiedDependency is Exception {
         is-core($name)
             ?? "{$name} is a builtin type, not an external module"
             !! "Could not find $.specification at line $line in:\n"
-                ~ $*REPO.repo-chain.map(*.Str).join("\n").indent(4)
+                ~ $*REPO.repo-chain.map(*.path-spec).join("\n").indent(4)
                 ~ ($.specification ~~ / $<name>=.+ '::from' $ /
                     ?? "\n\nIf you meant to use the :from adverb, use"
                         ~ " a single colon for it: $<name>:from<...>\n"