Update exception name due to breaking changes introduced in mongoengine 0.19.0.

lms/djangoapps/dashboard/git_import.py

@@ -335,7 +335,7 @@ def add_repo(repo, rdir_in, branch=None):
             mdb = mongoengine.connect(mongo_db['db'], host=mongouri)
         else:
             mdb = mongoengine.connect(mongo_db['db'], host=mongo_db['host'], port=mongo_db['port'])
-    except mongoengine.connection.ConnectionError:
+    except mongoengine.connection.ConnectionFailure:
         log.exception('Unable to connect to mongodb to save log, please '
                       'check MONGODB_LOG settings')
     cil = CourseImportLog(

lms/djangoapps/dashboard/tests/test_sysadmin.py

@@ -128,7 +128,7 @@ class TestSysAdminMongoCourseImport(SysadminBaseTestCase):
         try:
             mongoengine.connect(TEST_MONGODB_LOG['db'])
             CourseImportLog.objects.all().delete()
-        except mongoengine.connection.ConnectionError:
+        except mongoengine.connection.ConnectionFailure:
             pass
 
     def _setstaff_login(self):