Refactor get and post logic into new GradingService

lms/djangoapps/open_ended_grading/grading_service.py

-# This class gives a common interface for logging into
-# the graing controller
+# This class gives a common interface for logging into the grading controller
 import json
 import logging
 import requests
@@ -45,6 +44,35 @@ class GradingService(object):
 
         return response.json
 
+    def post(self, url, allow_redirects, data): 
+        """
+        Make a post request to the grading controller
+        """
+        try:
+            op = lambda: self.session.post(url, data=data,
+                                           allow_redirects=allow_redirects)
+            r = self._try_with_login(op)
+        except (RequestException, ConnectionError, HTTPError) as err:
+            # reraise as promised GradingServiceError, but preserve stacktrace.
+            raise GradingServiceError, str(err), sys.exc_info()[2]
+
+        return r.text
+
+    def get(self, url, allow_redirects, params):
+        """
+        Make a get request to the grading controller
+        """
+        op = lambda: self.session.get(url,
+                                      allow_redirects=allow_redirects,
+                                      params=params)
+        try:
+            r = self._try_with_login(op)
+        except (RequestException, ConnectionError, HTTPError) as err:
+            # reraise as promised GradingServiceError, but preserve stacktrace.
+            raise GradingServiceError, str(err), sys.exc_info()[2]
+
+        return r.text
+        
 
     def _try_with_login(self, operation):
         """

lms/djangoapps/open_ended_grading/staff_grading_service.py

@@ -83,17 +83,8 @@ class StaffGradingService(GradingService):
         Raises:
             GradingServiceError: something went wrong with the connection.
         """
-        op = lambda: self.session.get(self.get_problem_list_url,
-                                        allow_redirects = False,
-                                        params={'course_id': course_id,
-                                            'grader_id': grader_id})
-        try:
-            r = self._try_with_login(op)
-        except (RequestException, ConnectionError, HTTPError) as err:
-            # reraise as promised GradingServiceError, but preserve stacktrace.
-            raise GradingServiceError, str(err), sys.exc_info()[2]
-
-        return r.text
+        params = {'course_id': course_id,'grader_id': grader_id}
+        return self.get(self.get_problem_list_url, False, params)
 
 
     def get_next(self, course_id, location, grader_id):
@@ -114,17 +105,10 @@ class StaffGradingService(GradingService):
         Raises:
             GradingServiceError: something went wrong with the connection.
         """
-        op = lambda: self.session.get(self.get_next_url,
+        return self.get(self.get_next_url,
                                       allow_redirects=False,
                                       params={'location': location,
                                               'grader_id': grader_id})
-        try:
-            r = self._try_with_login(op)
-        except (RequestException, ConnectionError, HTTPError) as err:
-            # reraise as promised GradingServiceError, but preserve stacktrace.
-            raise GradingServiceError, str(err), sys.exc_info()[2]
-
-        return r.text
 
 
     def save_grade(self, course_id, grader_id, submission_id, score, feedback, skipped):
@@ -139,22 +123,15 @@ class StaffGradingService(GradingService):
         Raises:
             GradingServiceError if there's a problem connecting.
         """
-        try:
-            data = {'course_id': course_id,
-                    'submission_id': submission_id,
-                    'score': score,
-                    'feedback': feedback,
-                    'grader_id': grader_id,
-                    'skipped': skipped}
-
-            op = lambda: self.session.post(self.save_grade_url, data=data,
-                                           allow_redirects=False)
-            r = self._try_with_login(op)
-        except (RequestException, ConnectionError, HTTPError) as err:
-            # reraise as promised GradingServiceError, but preserve stacktrace.
-            raise GradingServiceError, str(err), sys.exc_info()[2]
-
-        return r.text
+        data = {'course_id': course_id,
+                'submission_id': submission_id,
+                'score': score,
+                'feedback': feedback,
+                'grader_id': grader_id,
+                'skipped': skipped}
+
+        return self.post(self.save_grade_url, data=data,
+                                       allow_redirects=False)
 
 # don't initialize until staff_grading_service() is called--means that just
 # importing this file doesn't create objects that may not have the right config