[1.5.x] Fixed #19367 -- Fixed saving ContentFile in filesystem storage

This was not working properly when ContentFile was initialized with
an unicode string.
Thanks Alexey Boriskin for the report and the test.

Backport of 34dcf51e06 from master.

tests/regressiontests/file_storage/tests.py

@@ -560,6 +560,13 @@ class InconsistentGetImageDimensionsBug(unittest.TestCase):
 
 class ContentFileTestCase(unittest.TestCase):
 
+    def setUp(self):
+        self.storage_dir = tempfile.mkdtemp()
+        self.storage = FileSystemStorage(self.storage_dir)
+
+    def tearDown(self):
+        shutil.rmtree(self.storage_dir)
+
     def test_content_file_default_name(self):
         self.assertEqual(ContentFile(b"content").name, None)
 
@@ -576,7 +583,18 @@ class ContentFileTestCase(unittest.TestCase):
         retrieved content is of the same type.
         """
         self.assertTrue(isinstance(ContentFile(b"content").read(), bytes))
-        self.assertTrue(isinstance(ContentFile("español").read(), six.text_type))
+        if six.PY3:
+            self.assertTrue(isinstance(ContentFile("español").read(), six.text_type))
+        else:
+            self.assertTrue(isinstance(ContentFile("español").read(), bytes))
+
+    def test_content_saving(self):
+        """
+        Test that ContentFile can be saved correctly with the filesystem storage,
+        both if it was initialized with string or unicode content"""
+        self.storage.save('bytes.txt', ContentFile(b"content"))
+        self.storage.save('unicode.txt', ContentFile("español"))
+
 
 class NoNameFileTestCase(unittest.TestCase):
     """