Fixed unicode error in CSV grade report generation.

TNL-1196

lms/djangoapps/instructor_task/tasks_helper.py

@@ -572,8 +572,7 @@ def upload_grades_csv(_xmodule_instance_args, _entry_id, course_id, _task_input,
             # We were able to successfully grade this student for this course.
             task_progress.succeeded += 1
             if not header:
-                # Encode the header row in utf-8 encoding in case there are unicode characters
-                header = [section['label'].encode('utf-8') for section in gradeset[u'section_breakdown']]
+                header = [section['label'] for section in gradeset[u'section_breakdown']]
                 rows.append(
                     ["id", "email", "username", "grade"] + header + cohorts_header + group_configs_header
                 )

lms/djangoapps/instructor_task/tests/test_tasks_helper.py

@@ -139,6 +139,23 @@ class TestInstructorGradeReport(TestReportMixin, InstructorTaskCourseTestCase):
         _groups = [group.name for group in self.course.user_partitions[0].groups]
         self.assertEqual(_groups, user_groups)
 
+    @patch('instructor_task.tasks_helper._get_current_task')
+    @patch('instructor_task.tasks_helper.iterate_grades_for')
+    def test_unicode_in_csv_header(self, mock_iterate_grades_for, _mock_current_task):
+        """
+        Tests that CSV grade report works if unicode in headers.
+        """
+        # mock a response from `iterate_grades_for`
+        mock_iterate_grades_for.return_value = [
+            (
+                self.create_student('username', 'student@example.com'),
+                {'section_breakdown': [{'label': u'\u8282\u540e\u9898 01'}], 'percent': 0},
+                'Cannot grade student'
+            )
+        ]
+        result = upload_grades_csv(None, None, self.course.id, None, 'graded')
+        self.assertDictContainsSubset({'attempted': 1, 'succeeded': 1, 'failed': 0}, result)
+
 
 @ddt.ddt
 class TestStudentReport(TestReportMixin, InstructorTaskCourseTestCase):