Install slapos.cookbook in python2.6

It allows to fetch all required depdendencies.

software/erp5/software.cfg

@@ -12,6 +12,7 @@ parts +=
 # Local development
   slapos.cookbook-repository
   check-recipe
+  slapos.cookbook-python2.6
 # Create instance template
   template
   validator
@@ -35,6 +36,12 @@ stop-on-error = true
 update-command = ${:command}
 command = grep parts ${buildout:develop-eggs-directory}/slapos.cookbook.egg-link
 
+[slapos.cookbook-python2.6]
+recipe = zc.recipe.egg
+eggs = slapos.cookbook
+scripts =
+python = python2.6
+
 [template-mariadb]
 recipe = slapos.recipe.template
 url = ${:_profile_base_location_}/instance-mariadb.cfg