Merge pull request joestump#221 from martyni/master

bug fix

Author: jaitaiwan

oauth2/__init__.py

@@ -491,6 +491,8 @@ def sign_request(self, signature_method, consumer, token):
             # section 4.1.1 "OAuth Consumers MUST NOT include an
             # oauth_body_hash parameter on requests with form-encoded
             # request bodies."
+            if not self.body:
+               self.body = ''
             self['oauth_body_hash'] = base64.b64encode(sha1(to_utf8(self.body)).digest())
 
         if 'oauth_consumer_key' not in self: