Fixed #8641: Documented the fact that file-saving methods must receive a File instance

git-svn-id: http://code.djangoproject.com/svn/django/trunk@8759 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/ref/files/file.txt

@@ -110,6 +110,9 @@ are the same as this one line::
 
     >>> car.photo.save('myphoto.jpg', contents, save=True)
 
+Note that the ``content`` argument must be an instance of
+:class:`File` or of a subclass of :class:`File`.
+
 ``File.delete(save=True)``
 ~~~~~~~~~~~~~~~~~~~~~~~~~~
 

docs/ref/files/storage.txt

@@ -42,6 +42,10 @@ If there already exists a file with this name ``name``, the storage system may
 modify the filename as necessary to get a unique name. The actual name of the
 stored file will be returned.
 
+The ``content`` argument must be an instance of
+:class:`django.db.files.File` or of a subclass of
+:class:`~django.db.files.File`.
+
 ``Storage.delete(name)``
 ~~~~~~~~~~~~~~~~~~~~~~~~