Resolve "Received 500 on export Student Scores"

Closes #140 (closed)

util/importer.py

@@ -253,10 +253,9 @@ def do_load_submission_types():
 def do_load_module_descriptions():
 
     print('''
-    This loader imports descriptions of modules in an exam. This step is purely
-    optional -- Grady works just fine without these information. If you want to
-    distinguish students within one instance or give information about the
-    grading type you should provide this info.
+    This loader imports descriptions of modules in an exam. This information
+    is used to distinguish students within one instance or give information
+    about the grading type.
 
     CSV file format: module_reference, total_score, pass_score, pass_only
 
@@ -377,8 +376,9 @@ def do_load_submissions():
     file = i('Get me the file with all the submissions',
              'submissions.json', is_file=True)
 
-    exam_obj = {}
-    if ExamType.objects.all():
+    if not ExamType.objects.all():
+        raise Exception('Modules need to be loaded before submissions.')
+    else:
         exam_query_set = ExamType.objects.all()
         print('Please select the corresponding module')
         print('You have the following choices:\n')
@@ -387,7+387,7 @@
         print()
 
         exam_prompt_key = i('Choose wisely')
         exam_obj = {'exam': exam_query_set[int(exam_prompt_key)]}
 
     with open(file) as exam_data_file:
         exam_data = json.JSONDecoder().decode(exam_data_file.read())