Fix Django deprecation warning

Django 1.9 deprecates passing a context directly to the render function
in template loader. This commit creates a proper template rendering
context before rendering the mails sent from the contact form.

gnuviechadmin/contact_form/forms.py

@@ -52,11 +52,16 @@ class ContactForm(forms.Form):
             self.request, dict(self.cleaned_data, site=site))
 
     def message(self):
-        return loader.render_to_string(self.template_name, self.get_context())
+        context = self.get_context()
+        template_context = context.flatten()
+        template_context.update({
+            'remote_ip': context.request.META['REMOTE_ADDR']
+        })
+        return loader.render_to_string(self.template_name, template_context)
 
     def subject(self):
-        subject = loader.render_to_string(
-            self.subject_template_name, self.get_context())
+        context = self.get_context().flatten()
+        subject = loader.render_to_string(self.subject_template_name, context)
         return ''.join(subject.splitlines())
 
     def save(self, fail_silently=False):

gnuviechadmin/templates/contact_form/contact_form.txt

@@ -1,4 +1,4 @@
-User {{ name }} <{{ email }}> from IP address {{ request.META.REMOTE_ADDR }}
+User {{ name }} <{{ email }}> from IP address {{ remote_ip }}
 sent the following message via the contact form at
 {{ site }}{% url 'contact_form' %}: