Do not treat streaming errors as file errors, closes #13323

Author: josevalim

lib/elixir/lib/io/stream.ex

@@ -1,11 +1,9 @@
 defmodule IO.StreamError do
-  defexception [:reason, :message]
+  defexception [:reason]
 
   @impl true
-  def exception(opts) do
-    reason = opts[:reason]
-    formatted = IO.iodata_to_binary(:file.format_error(reason))
-    %IO.StreamError{message: "error during streaming: #{formatted}", reason: reason}
+  def message(%{reason: reason}) do
+    "error during streaming: #{inspect(reason)}"
   end
 end
 

lib/elixir/test/elixir/string_io_test.exs

@@ -267,7 +267,7 @@ defmodule StringIOTest do
   test "IO.stream with invalid UTF-8" do
     {:ok, pid} = StringIO.open(<<130, 227, 129, 132, 227, 129, 134>>)
 
-    assert_raise IO.StreamError, fn ->
+    assert_raise IO.StreamError, "error during streaming: :invalid_unicode", fn ->
       IO.stream(pid, 2) |> Enum.to_list()
     end