[1.6.x] Fixed #22107 -- Fixed django.core.files.File object iteration.

Due to a mixup between text and bytes, iteration over
a File instance was broken under Python 3.

Thanks to trac user pdewacht for the report and patch.

Backport of 3841feee86 from master.

django/core/files/base.py

@@ -103,7 +103,7 @@ class File(FileProxyMixin):
 
                 # If this is the end of a line, yield
                 # otherwise, wait for the next round
-                if line[-1] in ('\n', '\r'):
+                if line[-1:] in (b'\n', b'\r'):
                     yield line
                 else:
                     buffer_ = line

tests/files/tests.py

@@ -1,5 +1,6 @@
 from __future__ import absolute_import
 
+from io import BytesIO
 import os
 import gzip
 import shutil
@@ -164,6 +165,14 @@ class FileTests(unittest.TestCase):
         self.assertFalse(hasattr(file, 'mode'))
         g = gzip.GzipFile(fileobj=file)
 
+    def test_file_iteration(self):
+        """
+        File objects should yield lines when iterated over.
+        Refs #22107.
+        """
+        file = File(BytesIO(b'one\ntwo\nthree'))
+        self.assertEqual(list(file), [b'one\n', b'two\n', b'three'])
+
 
 class FileMoveSafeTests(unittest.TestCase):
     def test_file_move_overwrite(self):