Fix bug while edit unicode title of item

Author: saltduck

market/contracts.py

@@ -923,6 +923,8 @@ def save(self):
         with open(file_path, 'w') as outfile:
             outfile.write(json.dumps(self.contract, indent=4))
 
+        if isinstance(self.previous_title, unicode):
+            self.previous_title = self.previous_title.encode('utf8')
         if self.previous_title and self.previous_title != self.contract["vendor_offer"]["listing"]["item"]["title"]:
             old_name = str(self.previous_title[:100])
             old_name = re.sub(r"[^\w\s]", '', file_name)