Fix tests on Python 2.6

Fixes #14 and #15.

setup.py

@@ -98,7 +98,7 @@ if __name__ == "__main__":
         install_requires=[
         ],
         tests_require=[
-            "pytest",
+            "pytest>=2.7.2",  # see https://github.com/hynek/attrs/issues/14
             "zope.interface",
         ],
         cmdclass={

tests/test_dunders.py

@@ -206,8 +206,10 @@ class TestAddInit(object):
         with pytest.raises(TypeError) as e:
             C(a=1, b=2)
 
-        msg = e.value if PY26 else e.value.args[0]
-        assert "__init__() got an unexpected keyword argument 'a'" == msg
+        assert (
+            "__init__() got an unexpected keyword argument 'a'" ==
+            e.value.args[0]
+        )
 
     def test_sets_attributes(self):
         """