Improve reading in error message

Signed-off-by: José Valim <jose.valim@plataformatec.com.br>

Author: José Valim

lib/elixir/lib/exception.ex

@@ -647,7 +647,7 @@ defmodule UndefinedFunctionError do
   def message(%{reason: :"function not exported",  module: module, function: function, arity: arity, exports: exports}) do
     suffix =
       if macro_exported?(module, function, arity) do
-        " but #{inspect(module)} defines a macro with the same name and arity." <>
+        ". However there is a macro with the same name and arity." <>
           " Be sure to require #{inspect(module)} if you intend to invoke this macro"
       else
         did_you_mean(module, function, arity, exports)

lib/elixir/test/elixir/exception_test.exs

@@ -386,8 +386,9 @@ defmodule ExceptionTest do
   end
 
   test "UndefinedFunctionError when the mfa is a macro but require wasn't called" do
+    _ = Code.ensure_loaded(Integer)
     assert %UndefinedFunctionError{module: Integer, function: :is_odd, arity: 1} |> message ==
-           "function Integer.is_odd/1 is undefined or private but Integer defines " <>
+           "function Integer.is_odd/1 is undefined or private. However there is " <>
            "a macro with the same name and arity. Be sure to require Integer if " <>
            "you intend to invoke this macro"
   end