bpo-34864: warn if "Prefer tabs when opening documents" set to "Always" (#10464)

* bpo-34864: warn if "Prefer tabs when opening documents" set to "Always"

* add NEWS entry

* address code review comments

* address second code review comments

* Add entry for idlelib/NEWS.txt.
diff --git a/Lib/idlelib/outwin.py b/Lib/idlelib/outwin.py
index 4af9f1a..e962142 100644
--- a/Lib/idlelib/outwin.py
+++ b/Lib/idlelib/outwin.py
@@ -109,7 +109,7 @@
         Return:
             Length of text inserted.
         """
-        if isinstance(s, (bytes, bytes)):
+        if isinstance(s, bytes):
             s = s.decode(iomenu.encoding, "replace")
         self.text.insert(mark, s, tags)
         self.text.see(mark)