Fixed string formatting for Python 2.6 in tests.

Updated Travis Python 2.7 version to 2.7.6.
More excludes.

.travis.yml

@@ -2,7 +2,7 @@ language: python
 
 python:
     - "2.6"
-    - "2.7"
+    - "2.7.6"
     - "3.4"
 
 env:
@@ -17,6 +17,10 @@ branches:
 
 matrix:
     exclude:
+        -
+            python: "2.6"
+            env: DJANGO_VERSION=1.5.10 SAMPLE_PROJECT=sample_project
+
         -
             python: "2.6"
             env: DJANGO_VERSION=1.7 SAMPLE_PROJECT=sample_project
@@ -25,6 +29,10 @@ matrix:
             python: "2.6"
             env: DJANGO_VERSION=1.7 SAMPLE_PROJECT=python3_sample_project
 
+        -
+            python: "2.7"
+            env: DJANGO_VERSION=1.5.10 SAMPLE_PROJECT=sample_project
+
         -
             python: "2.7"
             env: DJANGO_VERSION=1.7 SAMPLE_PROJECT=python3_sample_project

sample_project/app/tests.py

@@ -162,10 +162,10 @@ class SortableTestCase(TestCase):
         result = self.first_person.get_next()
 
         self.assertEqual(self.second_person, result, 'Next person should '
-            'be "{}"'.format(self.second_person))
+            'be "{0}"'.format(self.second_person))
 
     def test_get_previous(self):
         result = self.second_person.get_previous()
 
         self.assertEqual(self.first_person, result, 'Previous person should '
-            'be "{}"'.format(self.first_person))
+            'be "{0}"'.format(self.first_person))