hacking: noqa cleanup in horizon

attribute-level imports are not checked by hacking module now.
most noqa is used to disable warnings on attribute-level imports.
This commit drops noqa for this purpose.

After this, there are 8 noqa under horizon/ :)

In addition to this, the following changes are made.

horizon/exceptions.py: The following imports are dropped.
They are not used anywhere.
  from django.http import HttpRequest
  from django.views.debug import CLEANSED_SUBSTITUTE

horizon/forms/__init__.py:
Some entries were missing in __all__. They are added.

Change-Id: I33b504ef6c396f0675e8a340867e2ca59c77c684

1 files changed, 1 insertions, 1 deletions

diff --git a/manage.py b/manage.py
index 5818a6de3..df691be77 100755
--- a/manage.py
+++ b/manage.py
@@ -15,7 +15,7 @@
 import os
 import sys
 
-from django.core.management import execute_from_command_line  # noqa
+from django.core.management import execute_from_command_line
 
 if __name__ == "__main__":
     os.environ.setdefault("DJANGO_SETTINGS_MODULE",