Revert PR #708.

https://github.com/letsencrypt/letsencrypt/pull/708 broke the Boulder CI build
because Travis runs Ubuntu 12.04, which has an older setuptools. See
https://github.com/letsencrypt/boulder/issues/681.

letsencrypt-compatibility-test/setup.py

@@ -1,5 +1,3 @@
-import sys
-
 from setuptools import setup
 from setuptools import find_packages
 
@@ -9,14 +7,10 @@ install_requires = [
     'letsencrypt-apache',
     'letsencrypt-nginx',
     'docker-py',
+    'mock<1.1.0',  # py26
     'zope.interface',
 ]
 
-if sys.version_info < (2, 7):
-    install_requires.append('mock<1.1.0')
-else:
-    install_requires.append('mock')
-
 setup(
     name='letsencrypt-compatibility-test',
     packages=find_packages(),