Move real_name to UserProfile;

Delete student_id field;
Mark the problems that have submission;
Alter dispatcher to adapt the changes.

utils/captcha/__init__.py

@@ -82,10 +82,7 @@ class Captcha(object):
             x += font_size * random.randrange(6, 8) / 10
 
         self.django_request.session[self.session_key] = "".join(code)
-        with BytesIO() as buf:
-            image.save(buf, "gif")
-            buf_str = buf.getvalue()
-        return buf_str
+        return image
 
     def check(self, code):
         """

utils/captcha/views.py

@@ -2,10 +2,9 @@ from base64 import b64encode
 
 from . import Captcha
 from ..api import APIView
+from ..shortcuts import img2base64
 
 
 class CaptchaAPIView(APIView):
     def get(self, request):
-        img_prefix = "data:image/png;base64,"
-        img = img_prefix + b64encode(Captcha(request).get()).decode("utf-8")
-        return self.success(img)
+        return self.success(img2base64(Captcha(request).get()))