Use @coderanger's suggested way(#r5274401) to check setuptools are installed.

ka2n · ka2n · commit 8e5de719b2b5 · 2013-07-23T15:44:26.000+09:00
diff --git a/recipes/pip.rb b/recipes/pip.rb
@@ -60,7 +60,7 @@
   command <<-EOF
   #{node['python']['binary']} ez_setup.py
   EOF
-  not_if { ::File.exists?(ez_binary) }
+  not_if "#{node['python']['binary']} -c 'import setuptools'"
 end
 
 execute "install-pip" do
