old_contents: # vim: tabstop=4 shiftwidth=4 softtabstop=4
  
  # Copyright 2013 OpenStack Foundation.
  # All Rights Reserved.
  #
  #    Licensed under the Apache License, Version 2.0 (the "License"); you may
  #    not use this file except in compliance with the License. You may obtain
  #    a copy of the License at
  #
  #         http://www.apache.org/licenses/LICENSE-2.0
  #
  #    Unless required by applicable law or agreed to in writing, software
  #    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  #    License for the specific language governing permissions and limitations
  #    under the License.
  
  import os
  
  
  class HostDriver(object):
  
      def get_all_block_devices(self):
          """Get the list of all block devices seen in /dev/disk/by-path/."""
          dir = "/dev/disk/by-path/"
          files = os.listdir(dir)
          devices = []
          for file in files:
              devices.append(dir + file)
          return devices
  
new_contents: # vim: tabstop=4 shiftwidth=4 softtabstop=4
  
  # Copyright 2013 OpenStack Foundation.
  # All Rights Reserved.
  #
  #    Licensed under the Apache License, Version 2.0 (the "License"); you may
  #    not use this file except in compliance with the License. You may obtain
  #    a copy of the License at
  #
  #         http://www.apache.org/licenses/LICENSE-2.0
  #
  #    Unless required by applicable law or agreed to in writing, software
  #    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  #    License for the specific language governing permissions and limitations
  #    under the License.
  
  import os
  
  
  class HostDriver(object):
  
      def get_all_block_devices(self):
          """Get the list of all block devices seen in /dev/disk/by-path/."""
          files = []
          dir = "/dev/disk/by-path/"
          if os.path.isdir(dir):
              files = os.listdir(dir)
          devices = []
          for file in files:
              devices.append(dir + file)
          return devices
  
subject: Check if dir exists before calling listdir