skip serialization tests if simplejson module is not available

--HG--
extra : convert_revision : svn%3Ab85faa78-f9eb-468e-a121-7cced6da292c%401048

scrapy/trunk/scrapy/tests/test_serialization.py

@@ -1,9 +1,16 @@
-import unittest
-from scrapy.utils.serialization import serialize, unserialize, serialize_funcs
+from twisted.trial import unittest
 
 class SerializationTest(unittest.TestCase):
+
+    def setUp(self):
+        try:
+            import simplejson
+        except ImportError, e:
+            raise unittest.SkipTest(e)
+
     def test_string_serialization(self):
         """Test simple string serialization"""
+        from scrapy.utils.serialization import serialize, unserialize, serialize_funcs
 
         s = "string to serialize"
         for format in serialize_funcs.iterkeys():
@@ -11,6 +18,7 @@ class SerializationTest(unittest.TestCase):
 
     def test_dict_serialization(self):
         """Test dict serialization"""
+        from scrapy.utils.serialization import serialize, unserialize, serialize_funcs
 
         # using only string keys/values since it's the only data type that
         # works with all serializers