Simplify how shards are selected in CI

lms/djangoapps/courseware/tests/test_submitting_problems.py

@@ -303,7 +303,7 @@ class TestSubmittingProblems(ModuleStoreTestCase, LoginEnrollmentTestCase, Probl
         return [s.earned for s in hw_section['scores']]
 
 
-@attr('shard_3')
+@attr(shard=3)
 class TestCourseGrader(TestSubmittingProblems):
     """
     Suite of tests for the course grader.
@@ -682,7 +682,7 @@ class TestCourseGrader(TestSubmittingProblems):
         self.assertEqual(req_status[0]["status"], 'satisfied')
 
 
-@attr('shard_1')
+@attr(shard=1)
 class ProblemWithUploadedFilesTest(TestSubmittingProblems):
     """Tests of problems with uploaded files."""
     # Tell Django to clean out all databases, not just default
@@ -737,7 +737,7 @@ class ProblemWithUploadedFilesTest(TestSubmittingProblems):
         self.assertItemsEqual(kwargs['files'].keys(), filenames.split())
 
 
-@attr('shard_1')
+@attr(shard=1)
 class TestPythonGradedResponse(TestSubmittingProblems):
     """
     Check that we can submit a schematic and custom response, and it answers properly.
@@ -988,7 +988,7 @@ class TestPythonGradedResponse(TestSubmittingProblems):
         self._check_ireset(name)
 
 
-@attr('shard_1')
+@attr(shard=1)
 class TestConditionalContent(TestSubmittingProblems):
     """
     Check that conditional content works correctly with grading.