old_contents: from fabric.api import env
  
  
  class Integration(object):
      def setup(self):
          env.host_string = "127.0.0.1"
  
new_contents: from fabric.api import env
  
  
  class Integration(object):
      def setup(self):
          if not env.host_string: # Allow runtime selection
              env.host_string = "127.0.0.1"
  
subject: Allow easy local exec of integration suite via eg -H