Fix tweepy.API.update_with_media

If filename is an instance of `unicode',
L.76 `` 'Content-Disposition: form-data; name="%s"; filename="%s"' % (form_field, filename) ''
must be unicode string.

Because of it, L. 803 `` body = '\r\n'.join(body) '' fails.

Therefore, I made `filename' designed to be percent-encoded str object
before formatting.

tweepy/api.py

@@ -4,6 +4,7 @@
 
 import os
 import mimetypes
+import urllib
 
 from tweepy.binder import bind_api
 from tweepy.error import TweepError
@@ -788,6 +789,8 @@ class API(object):
         if file_type not in ['image/gif', 'image/jpeg', 'image/png']:
             raise TweepError('Invalid file type for image: %s' % file_type)
 
+        if isinstance(filename, unicode):
+          filename = urllib.quote(filename.encode("utf-8"))
 
 
         BOUNDARY = 'Tw3ePy'