Properly skipped yaml tests when not installed

tests/serializers/tests.py

@@ -5,6 +5,12 @@ import json
 from datetime import datetime
 import unittest
 from xml.dom import minidom
+try:
+    import yaml
+    HAS_YAML = True
+except ImportError:
+    HAS_YAML = False
+
 
 from django.conf import settings
 from django.core import serializers
@@ -445,12 +451,9 @@ class JsonSerializerTransactionTestCase(SerializersTransactionTestBase, Transact
         }
     }]"""
 
-try:
-    import yaml
-except ImportError:
-    pass
-else:
-    class YamlSerializerTestCase(SerializersTestBase, TestCase):
+
+@unittest.skipUnless(HAS_YAML, "No yaml library detected")
+class YamlSerializerTestCase(SerializersTestBase, TestCase):
     serializer_name = "yaml"
     fwd_ref_str = """- fields:
     headline: Forward references pose no problem
@@ -509,7 +512,9 @@ else:
                     ret_list.append(str(field_value))
         return ret_list
 
-    class YamlSerializerTransactionTestCase(SerializersTransactionTestBase, TransactionTestCase):
+
+@unittest.skipUnless(HAS_YAML, "No yaml library detected")
+class YamlSerializerTransactionTestCase(SerializersTransactionTestBase, TransactionTestCase):
     serializer_name = "yaml"
     fwd_ref_str = """- fields:
     headline: Forward references pose no problem