Rip out all the u"..." literals and calls to unicode().
diff --git a/Lib/email/generator.py b/Lib/email/generator.py
index 4f3fea4..02b4495 100644
--- a/Lib/email/generator.py
+++ b/Lib/email/generator.py
@@ -23,7 +23,7 @@
 def _is8bitstring(s):
     if isinstance(s, str):
         try:
-            unicode(s, 'us-ascii')
+            str(s, 'us-ascii')
         except UnicodeError:
             return True
     return False