Issue #16714: use 'raise' exceptions, don't 'throw'.

Patch by Serhiy Storchaka.
diff --git a/Lib/email/utils.py b/Lib/email/utils.py
index 6b6d7f4..93a625c 100644
--- a/Lib/email/utils.py
+++ b/Lib/email/utils.py
@@ -83,7 +83,7 @@
     'utf-8'.
     """
     name, address = pair
-    # The address MUST (per RFC) be ascii, so throw a UnicodeError if it isn't.
+    # The address MUST (per RFC) be ascii, so raise an UnicodeError if it isn't.
     address.encode('ascii')
     if name:
         try: