Make compatible with Django 1.10 and 1.11

Removes use of future tag (not available in Django 1.10+).
Flatten Context into dict for render (necessary for Django 1.11+).

Both changes compatible with Django >= 1.8.

Change-Id: I5db4af45208423753dd5d60616ee781e6471b9e6
Closes-bug: 1816707

congress_dashboard/datasources/templates/datasources/_create.html

@@ -1,6 +1,5 @@
 {% extends "horizon/common/_modal_form.html" %}
 {% load i18n %}
-{% load url from future %}
 
 {% block form_id %}create_datasource_form{% endblock %}
 {% block form_action %}{% url 'horizon:admin:datasources:create' %}{% endblock %}

congress_dashboard/policies/rules/workflows.py

@@ -79,7 +79,7 @@ class CreateOutput(workflows.Step):
         columns_list = policy_columns.split(', ')
         context['policy_columns_list'] = columns_list
         context['policy_columns_count'] = len(columns_list)
-        return step_template.render(context)
+        return step_template.render(context.flatten())
 
 
 class CreateConditionsAction(workflows.Action):
@@ -170,7 +170,7 @@ class CreateConditions(workflows.Step):
         context['column_pattern_error'] = COLUMN_PATTERN_ERROR
         context['table_pattern'] = TABLE_PATTERN
         context['table_pattern_error'] = TABLE_PATTERN_ERROR
-        return step_template.render(context)
+        return step_template.render(context.flatten())
 
 
 def _underscore_slugify(name):

congress_dashboard/policies/templates/policies/_create.html

@@ -1,6 +1,5 @@
 {% extends "horizon/common/_modal_form.html" %}
 {% load i18n %}
-{% load url from future %}
 
 {% block form_id %}create_policy_form{% endblock %}
 {% block form_action %}{% url 'horizon:admin:policies:create' %}{% endblock %}

congress_dashboard/policies/templates/policies/rules/_create_raw.html

@@ -1,6 +1,5 @@
 {% extends "horizon/common/_modal_form.html" %}
 {% load i18n %}
-{% load url from future %}
 
 {% block form_id %}create_raw_rule_form{% endblock %}
 {% block form_action %}{% url 'horizon:admin:policies:create_raw_rule' policy_name %}{% endblock %}