fix setup.py regarding pathlib

setup.py

 #!/usr/bin/env python
 
 import os
+import sys
 
 from setuptools import setup
 
@@ -11,6 +12,9 @@ name = 'rubygemsrecipe'
 def read(*rnames):
     return open(os.path.join(os.path.dirname(__file__), *rnames)).read()
 
+test_requires=['mock']
+if sys.version_info < (3,4):
+    test_requires.append('pathlib')
 
 setup(name=name,
       version=version,
@@ -30,10 +34,7 @@ setup(name=name,
           'slapos.recipe.build',
       ],
       extras_require={
-          'test': [
-              'mock',
-              'pathlib; python_version<"3.4"',
-          ],
+          'test': test_requires
       },
       entry_points={
           'zc.buildout': ['default = rubygems:Recipe']