old_contents: # encoding: utf-8
  
  """
  .. codeauthor:: Tsuyoshi Hombashi <gogogo.vm@gmail.com>
  """
  
  from __future__ import absolute_import
  
  
  def verify_network_interface(device):
      try:
          import netifaces
      except ImportError:
          return
  
      if device not in netifaces.interfaces():
          raise ValueError("invalid network interface: " + device)
  
new_contents: # encoding: utf-8
  
  """
  .. codeauthor:: Tsuyoshi Hombashi <gogogo.vm@gmail.com>
  """
  
  from __future__ import absolute_import
  
  from ._error import NetworkInterfaceNotFoundError
  
  
  def verify_network_interface(device):
      try:
          import netifaces
      except ImportError:
          return
  
      if device not in netifaces.interfaces():
          raise NetworkInterfaceNotFoundError(
              "invalid network interface: " + device)
  
subject: Modify error