Fixed error message and comment.

cabal-install/Distribution/Client/Targets.hs

@@ -729,8 +729,9 @@ readUserConstraint str =
       Just c  -> Right c
   where
     msgCannotParse =
-         "expected a package name followed by a constraint, which is "
-      ++ "either a version range, 'installed', 'source' or flags"
+         "expected a (possibly qualified) package name followed by a " ++
+         "constraint, which is either a version range, 'installed', " ++
+         "'source', 'test', 'bench', or flags"
 
 instance Text UserConstraint where
   disp (UserConstraint qual name prop) =

cabal-install/Distribution/Solver/Types/PackagePath.hs

@@ -41,7 +41,7 @@ data Namespace =
 instance Binary Namespace
 
 -- | Pretty-prints a namespace. The result is either empty or
--- ends in a period, so it can be prepended onto a package name.
+-- ends in a period, so it can be prepended onto a qualifier.
 dispNamespace :: Namespace -> Disp.Doc
 dispNamespace DefaultNamespace = Disp.empty
 dispNamespace (Independent i) = Disp.int i <<>> Disp.text "."