Prevent JSON errors from raising an exception. The exception will be …

…logged.

edx_proctoring/backends/rest.py

@@ -338,5 +338,10 @@ def _make_attempt_request(self, exam, attempt, method='POST', status=None, **pay
         if method == 'GET':
             headers.update(self._get_language_headers())
         log.debug('Making %r attempt request at %r', method, url)
-        response = self.session.request(method, url, json=payload, headers=headers).json()
-        return response
+        response = self.session.request(method, url, json=payload, headers=headers)
+        try:
+            data = response.json()
+        except ValueError:
+            log.exception("Decoding attempt %r -> %r", attempt, response.content)
+            data = {}
+        return data

edx_proctoring/backends/tests/test_rest.py

@@ -242,6 +242,18 @@ def test_update_exam_attempt_status(self, provider_method_name, corresponding_st
         status = getattr(self.provider, provider_method_name)(self.backend_exam['external_id'], attempt_id)
         self.assertEqual(status, corresponding_status)
 
+    @responses.activate
+    def test_failed_json(self):
+        attempt_id = 2
+        responses.add(
+            responses.PATCH,
+            url=self.provider.exam_attempt_url.format(exam_id=self.backend_exam['external_id'], attempt_id=attempt_id),
+            body='"]'
+        )
+        status = self.provider.mark_erroneous_exam_attempt(self.backend_exam['external_id'], attempt_id)
+        # the important thing is that it didn't raise an exception for bad json
+        self.assertEqual(status, None)
+
     @responses.activate
     def test_remove_attempt(self):
         attempt_id = 2