From: Dmitry Shachnev <mitya57@gmail.com>
Subject: email: Add special case for latin texts

 In MIMEText class, use iso-8859-1 encoding by default if all the characters are
 in range(256). This makes the messages use quoted-printable transfer-encoding
 for most western-european languages.

 Update the tests accordingly.

Bug: http://bugs.python.org/issue15016

diff -ruN a/Lib/email/mime/text.py b/Lib/email/mime/text.py
--- a/Lib/email/mime/text.py	2012-06-06 12:30:13.866861588 +0400
+++ b/Lib/email/mime/text.py	2012-06-06 13:28:43.427552123 +0400
@@ -26,15 +26,24 @@
         Content-Transfer-Encoding header will also be set.
         """
 
-        # If no _charset was specified, check to see see if there are non-ascii
-        # characters present. If not, use 'us-ascii', otherwise use utf-8.
+        # If no _charset was specified, try to guess which encoding to use:
+        # - All the characters are in range(128) -> using us-ascii
+        # - All the characters are in range(256) -> using iso-8859-1
+        # - Else using utf-8
+        #
         # XXX: This can be removed once #7304 is fixed.
         if _charset is None:
             try:
                 _text.encode('us-ascii')
-                _charset = 'us-ascii'
             except UnicodeEncodeError:
-                _charset = 'utf-8'
+                try:
+                    _text.encode('iso-8859-1')
+                except UnicodeEncodeError:
+                    _charset = 'utf-8'
+                else:
+                    _charset = 'iso-8859-1'
+            else:
+                _charset = 'us-ascii'
 
         MIMENonMultipart.__init__(self, 'text', _subtype,
                                   **{'charset': _charset})
diff -ruN a/Lib/test/test_email/test_email.py b/Lib/test/test_email/test_email.py
--- a/Lib/test/test_email/test_email.py	2012-06-06 12:29:30.537759836 +0400
+++ b/Lib/test/test_email/test_email.py	2012-06-06 13:26:47.728596390 +0400
@@ -622,15 +622,26 @@
             abc
             """))
 
-    def test_unicode_body_defaults_to_utf8_encoding(self):
-        # Issue 14291
+    def test_latin_body_defaults_to_latin_encoding(self):
+        # Issue 15016
         m = MIMEText('É testabc\n')
         self.assertEqual(str(m),textwrap.dedent("""\
+            Content-Type: text/plain; charset="iso-8859-1"
+            MIME-Version: 1.0
+            Content-Transfer-Encoding: quoted-printable
+
+            =C9 testabc
+            """))
+
+    def test_non_latin_body_defaults_to_utf8_encoding(self):
+        # Issue 14291
+        m = MIMEText(chr(256)+' testabc\n')
+        self.assertEqual(str(m),textwrap.dedent("""\
             Content-Type: text/plain; charset="utf-8"
             MIME-Version: 1.0
             Content-Transfer-Encoding: base64
 
-            w4kgdGVzdGFiYwo=
+            xIAgdGVzdGFiYwo=
             """))