Fix minor bugs blocking report generation

Change-Id: I5c1d8f476587362b5d20d028aeb6283c4c3b18b0

edx/analytics/tasks/mapreduce.py

@@ -5,8 +5,6 @@ from __future__ import absolute_import
 
 import luigi.hadoop
 
-from stevedore import ExtensionManager
-
 
 class MapReduceJobTask(luigi.hadoop.JobTask):
     """
@@ -19,6 +17,10 @@ class MapReduceJobTask(luigi.hadoop.JobTask):
     )
 
     def job_runner(self):
+        # Lazily import this since this module will be loaded on hadoop worker nodes however stevedore will not be
+        # available in that environment.
+        from stevedore import ExtensionManager
+
         extension_manager = ExtensionManager('mapreduce.engine')
         try:
             engine_class = extension_manager[self.mapreduce_engine].plugin

edx/analytics/tasks/reports/tests/test_total_enrollments.py

@@ -237,6 +237,23 @@ class TestWeeklyAllUsersAndEnrollments(unittest.TestCase):
         self.assertEqual(res.loc[self.enrollment_label]['2013-01-08'], 4)
         self.assertEqual(res.loc[self.enrollment_label]['2013-01-15'], 6)
 
+    def test_blacklist_course_not_in_enrollments(self):
+        enrollments = """
+        course_1 2013-01-02 1
+        course_2 2013-01-02 2
+        course_3 2013-01-02 4
+        course_2 2013-01-09 1
+        course_3 2013-01-15 2
+        """
+        blacklist = """
+        course_4
+        course_1
+        course_2
+        """
+        res = self.run_task('', enrollments, '2013-01-15', 2, blacklist=blacklist)
+        self.assertEqual(res.loc[self.enrollment_label]['2013-01-08'], 4)
+        self.assertEqual(res.loc[self.enrollment_label]['2013-01-15'], 6)
+
     def test_unicode(self):
         course_id = u'course_\u2603'
 

edx/analytics/tasks/reports/total_enrollments.py

@@ -98,8 +98,13 @@ class AllCourseEnrollmentCountMixin(CourseEnrollmentCountMixin):
         Returns:
             None, the `course_data` is modified in place.
         """
+        for course_id in course_blacklist:
+            try:
                 # Drop from axis 1 because we are dropping columns, not rows.
-        course_data.drop(course_blacklist, axis=1, inplace=True)
+                course_data.drop(course_id, axis=1, inplace=True)
+            except ValueError:
+                # There is no column for this course.
+                pass
 
     def save_output(self, results, output_file):
         """