[#725, #630] Fix breaking of partner sites

Work around the SQL query that hangs by assembling the list of countries
in python instead.

Use prefetch_related() to (hopefully) minimize the number of queries
needed.

akvo/rsr/models/project.py

@@ -477,7 +477,13 @@ def all_partners(self):
 
         def countries(self):
             """Returns a Country queryset of the countries of these projects"""
-            return Country.objects.filter(projectlocation__project__in=self).distinct()
+            country_ids = []
+            for project in self:
+                for location in project.locations.all():
+                    country_ids.append(location.country.id)
+
+            country_ids = list(set(country_ids))
+            return Country.objects.filter(id__in=country_ids).distinct()
 
 
     def __unicode__(self):

akvo/rsr/views_partner_sites/base.py

@@ -60,12 +60,13 @@ def get_context_data(self, **kwargs):
 
     def get_queryset(self):
         partner_site = self.request.partner_site
-
         # Check if only projects of the partner should be shown or all projects
         if partner_site.partner_projects:
-            projects = get_object_or_404(Organisation, pk=self.request.organisation_id).published_projects()
+            projects = get_object_or_404(
+                    Organisation, pk=self.request.organisation_id
+                ).published_projects().prefetch_related('locations')
         else:
-            projects = Project.objects.all().published()
+            projects = Project.objects.all().published().prefetch_related('locations')
 
         # Check if keywords have been specified for the partner site and filter projects based on keywords if so
         if partner_site.keywords.all():