Tests: skip Solr content extraction with old PySolr

Until pysolr 3.1.1 ships there's no point in running the Solr content
extraction tests because they'll fail:

django-haystack/pysolr#104

Author: CubeXspark

tests/solr_tests/tests/test_solr_backend.py

@@ -1,26 +1,24 @@
 # -*- coding: utf-8 -*-
-from __future__ import print_function
-from __future__ import unicode_literals
+from __future__ import print_function, unicode_literals
+
 import datetime
-from decimal import Decimal
-import os
 import logging as std_logging
-
-from mock import patch
+import os
+from decimal import Decimal
 
 import pysolr
-
 from django.conf import settings
 from django.test import TestCase
-from haystack import connections, reset_search_queries
-from haystack import indexes
-from haystack.inputs import AutoQuery, AltParser, Raw
+from django.utils.unittest import skipIf
+from mock import patch
+
+from core.models import AFourthMockModel, AnotherMockModel, ASixthMockModel, MockModel
+from core.tests.mocks import MockSearchResult
+from haystack import connections, indexes, reset_search_queries
+from haystack.inputs import AltParser, AutoQuery, Raw
 from haystack.models import SearchResult
-from haystack.query import SearchQuerySet, RelatedSearchQuerySet, SQ
+from haystack.query import RelatedSearchQuerySet, SearchQuerySet, SQ
 from haystack.utils.loading import UnifiedIndex
-from core.models import (MockModel, AnotherMockModel,
-                         AFourthMockModel, ASixthMockModel)
-from core.tests.mocks import MockSearchResult
 
 test_pickling = True
 
@@ -1313,6 +1311,7 @@ def test_boost(self):
         ])
 
 
+@skipIf(pysolr.__version__ < (3, 1, 1), 'content extraction requires pysolr > 3.1.0')
 class LiveSolrContentExtractionTestCase(TestCase):
     def setUp(self):
         super(LiveSolrContentExtractionTestCase, self).setUp()