"Port" the fix for issue 1974 from the trunk (2.7).  Because Python 3.x does things much better, less changes are necessary.

This also shoves test_email_codecs_rename.py onto test_email_codecs.py even though the test needs to be ported to Python 3.
diff --git a/Lib/email/test/test_email.py b/Lib/email/test/test_email.py
index 8857e42..4b5065f 100644
--- a/Lib/email/test/test_email.py
+++ b/Lib/email/test/test_email.py
@@ -769,7 +769,7 @@
         msg['To'] = to
         eq(msg.as_string(maxheaderlen=78), '''\
 To: "Someone Test #A" <someone@eecs.umich.edu>,<someone@eecs.umich.edu>,
-\t"Someone Test #B" <someone@umich.edu>,
+ "Someone Test #B" <someone@umich.edu>,
  "Someone Test #C" <someone@eecs.umich.edu>,
  "Someone Test #D" <someone@eecs.umich.edu>
 
@@ -852,7 +852,7 @@
         # snug against the field name.
         eq(msg.as_string(maxheaderlen=78), """\
 Face-1:\x20
-\tiVBORw0KGgoAAAANSUhEUgAAADAAAAAwBAMAAAClLOS0AAAAGFBMVEUAAAAkHiJeRUIcGBi9
+ iVBORw0KGgoAAAANSUhEUgAAADAAAAAwBAMAAAClLOS0AAAAGFBMVEUAAAAkHiJeRUIcGBi9
  locQDQ4zJykFBAXJfWDjAAACYUlEQVR4nF2TQY/jIAyFc6lydlG5x8Nyp1Y69wj1PN2I5gzp
 Face-2:\x20
  iVBORw0KGgoAAAANSUhEUgAAADAAAAAwBAMAAAClLOS0AAAAGFBMVEUAAAAkHiJeRUIcGBi9