Fix most trivially-findable print statements.

There's one major and one minor category still unfixed:
doctests are the major category (and I hope to be able to augment the
refactoring tool to refactor bona fide doctests soon);
other code generating print statements in strings is the minor category.

(Oh, and I don't know if the compiler package works.)
diff --git a/Lib/email/iterators.py b/Lib/email/iterators.py
index e99f228..4f2c84c 100644
--- a/Lib/email/iterators.py
+++ b/Lib/email/iterators.py
@@ -63,11 +63,11 @@
     if fp is None:
         fp = sys.stdout
     tab = ' ' * (level * 4)
-    print >> fp, tab + msg.get_content_type(),
+    print(tab + msg.get_content_type(), end=' ', file=fp)
     if include_default:
-        print >> fp, '[%s]' % msg.get_default_type()
+        print('[%s]' % msg.get_default_type(), file=fp)
     else:
-        print >> fp
+        print(file=fp)
     if msg.is_multipart():
         for subpart in msg.get_payload():
             _structure(subpart, fp, level+1, include_default)