added pylint ignores, fixed missing import

(cherry picked from commit 273df4e113)

lms/envs/aws_migrate.py

@@ -4,9 +4,14 @@ database migrations, since we don't want to normally run the
 LMS with enough privileges to modify the database schema.
 """
 
+# We intentionally define lots of variables that aren't used, and
+# want to import all variables from base settings files
+# pylint: disable=W0401, W0614
+
 # Import everything from .aws so that our settings are based on those.
 from .aws import *
 import os
+from django.core.exceptions import ImproperlyConfigured
 
 USER = os.environ.get('DB_MIGRATION_USER', 'root')
 PASSWORD = os.environ.get('DB_MIGRATION_PASS', None)