Index: Lib/mailbox.py
===================================================================
--- Lib/mailbox.py	(Revision 58874)
+++ Lib/mailbox.py	(Arbeitskopie)
@@ -333,7 +333,7 @@
 
     def get_file(self, key):
         """Return a file-like representation or raise a KeyError."""
-        f = open(os.path.join(self._path, self._lookup(key)), 'rb')
+        f = open(os.path.join(self._path, self._lookup(key)), 'r')
         return _ProxyFile(f)
 
     def iterkeys(self):
@@ -936,7 +936,7 @@
     def get_file(self, key):
         """Return a file-like representation or raise a KeyError."""
         try:
-            f = open(os.path.join(self._path, str(key)), 'rb')
+            f = open(os.path.join(self._path, str(key)), 'r')
         except IOError as e:
             if e.errno == errno.ENOENT:
                 raise KeyError('No message with key: %s' % key)
Index: Lib/test/test_mailbox.py
===================================================================
--- Lib/test/test_mailbox.py	(Revision 58874)
+++ Lib/test/test_mailbox.py	(Arbeitskopie)
@@ -170,9 +170,9 @@
         key1 = self._box.add(_sample_message)
         data0 = self._box.get_file(key0).read()
         data1 = self._box.get_file(key1).read()
-        self.assertEqual(data0.decode().replace(os.linesep, '\n'),
+        self.assertEqual(data0.replace(os.linesep, '\n'),
                          self._template % 0)
-        self.assertEqual(data1.decode().replace(os.linesep, '\n'),
+        self.assertEqual(data1.replace(os.linesep, '\n'),
                          _sample_message)
 
     def test_iterkeys(self):