appengine: upload data to blob programmatically

gistfile1.py

PAYLOAD_TEMPLATE = \
"""--==boundary\r
Content-Disposition: form-data; name="file"; filename="%s"\r
Content-Type: %s\r
\r
%s\r
--==boundary--\r
"""

destination_url = blobstore.create_upload_url('/upload-sink')
headers = {
  'Content-Type': 'multipart/form-data; boundary="==boundary"',
}
image_bytes = open("test_image.jpg", "r").read()
payload = PAYLOAD_TEMPLATE % ('test_image.jpg',
                              'image/jpeg',
                              image_bytes)
result = urlfetch.fetch(
    destination_url,
    method='POST',
    headers=headers,
    payload=payload,
    follow_redirects=False,
    deadline=10.0)