Fixed #11150 -- Removed dependency on cStringIO in ImageField validation. Thanks vvd for the report.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@17825 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/forms/fields.py

@@ -577,8 +577,8 @@ class ImageField(FileField):
 
             # Since we're about to use the file again we have to reset the
             # file object if possible.
-            if hasattr(file, 'reset'):
+            if hasattr(file, 'seek') and callable(file.seek):
-                file.reset()
+                file.seek(0)
 
             # verify() is the only method that can spot a corrupt PNG,
             #  but it must be called immediately after the constructor

tests/modeltests/model_forms/tests.py

@@ -1370,6 +1370,19 @@ class OldFormForXTests(TestCase):
         self.assertEqual(instance.image.name, 'foo/test4.png')
         instance.delete()
 
+        # Test image field when cStringIO is not available
+        from django.forms import fields
+        from StringIO import StringIO
+        old_StringIO = fields.StringIO
+        fields.StringIO = StringIO
+        try:
+            f = ImageFileForm(
+                data={'description': u'An image'},
+                files={'image': SimpleUploadedFile('test.png', image_data)})
+            self.assertEqual(f.is_valid(), True)
+        finally:
+            fields.StringIO = old_StringIO
+
     def test_media_on_modelform(self):
         # Similar to a regular Form class you can define custom media to be used on
         # the ModelForm.