Index: Lib/email/test/test_email.py
===================================================================
--- Lib/email/test/test_email.py	(revision 85670)
+++ Lib/email/test/test_email.py	(working copy)
@@ -2590,13 +2590,14 @@
         eq(msg.get_payload(), "Here's the message body\n")
 
     def test_crlf_separation(self):
+        # msg_26.txt is a file that has \r\n line endings.
         eq = self.assertEqual
         with openfile('msg_26.txt', newline='\n') as fp:
             msg = Parser().parse(fp)
         eq(len(msg.get_payload()), 2)
         part1 = msg.get_payload(0)
         eq(part1.get_content_type(), 'text/plain')
-        eq(part1.get_payload(), 'Simple email with attachment.\r\n\r\n')
+        eq(part1.get_payload(), 'Simple email with attachment.\n\n')
         part2 = msg.get_payload(1)
         eq(part2.get_content_type(), 'application/riscos')
 
@@ -2931,6 +2932,27 @@
         m = bfp.close()
         self.assertEqual(str(m), self.latin_bin_msg_as7bit)
 
+    crlf_bin_msg = textwrap.dedent("""\
+        From: foo@bar.com\r
+        To: test\r
+        Mime-Version: 1.0\r
+        Content-Type: text/plain; charset="ascii"\r
+        \r
+        Body text\r
+        should translate\r
+        crlf\r
+        """).encode('ascii')
+
+    def test_bytes_parser_translates_crlf_input(self):
+        # Issue 10134: bytes input was not translating \r\n to \n.
+        # (See also issue 724459.)
+        m = email.message_from_bytes(self.crlf_bin_msg)
+        out = BytesIO()
+        email.generator.BytesGenerator(out).flatten(m)
+        self.assertEqual(out.getvalue(),
+                         self.crlf_bin_msg.replace(b'\r\n', b'\n'))
+
+
 
 class TestBytesGeneratorIdempotent(TestIdempotent):
 
@@ -2944,7 +2966,8 @@
         b = BytesIO()
         g = email.generator.BytesGenerator(b, maxheaderlen=0)
         g.flatten(msg)
-        self.assertEqual(data, b.getvalue())
+        # This isn't a true inversion; email translates \r\n into \n.
+        self.assertEqual(data.replace(b'\r\n', b'\n'), b.getvalue())
 
     maxDiff = None
 
Index: Lib/email/feedparser.py
===================================================================
--- Lib/email/feedparser.py	(revision 85670)
+++ Lib/email/feedparser.py	(working copy)
@@ -57,6 +57,7 @@
         self._eofstack = []
         # A flag indicating whether the file has been closed or not.
         self._closed = False
+        self._crlf_file = None
 
     def push_eof_matcher(self, pred):
         self._eofstack.append(pred)
@@ -78,6 +79,14 @@
         # Pop the line off the stack and see if it matches the current
         # false-EOF predicate.
         line = self._lines.pop()
+        # Assume the line ending of the first line parsed is the
+        # platform line ending.  After that, any time we see that
+        # ending we convert it to '\n', which is what email uses
+        # internally.
+        if self._crlf_file is None:
+            self._crlf_file = line.endswith('\r\n')
+        elif self._crlf_file and line.endswith('\r\n'):
+                line = line[:-2] + '\n'
         # RFC 2046, section 5.1.2 requires us to recognize outer level
         # boundaries at any level of inner nesting.  Do this, but be sure it's
         # in the order of most to least nested.