Log Message:
py-django: update to 1.11.6

Bugfixes:
* Made the CharField form field convert whitespace-only values to the \ 
empty_value when strip is enabled.
* Fixed crash when using the name of a model’s autogenerated primary key (id) \ 
in an Index’s fields.
* Fixed a regression in Django 1.9 where a custom view error handler such as \ 
handler404 that accesses csrf_token could cause CSRF verification failures on \ 
other pages