old_contents: # -*- coding: utf-8 -*-
  
  """
  byceps.util.system
  ~~~~~~~~~~~~~~~~~~
  
  :Copyright: 2006-2016 Jochen Kupperschmidt
  :License: Modified BSD, see LICENSE for details.
  """
  
  import os
  
  
  CONFIG_ENV_VAR_NAME = 'BYCEPS_CONFIG'
  
  
  def get_config_env_name_from_env(*, default=None):
      """Return the configuration environment name set via environment
      variable.
  
      Raise an exception if it isn't set.
      """
      env = os.environ.get(CONFIG_ENV_VAR_NAME)
  
      if env is None:
          if default is None:
              raise Exception(
                  "No configuration environment was specified via the '{}' "
                  "environment variable.".format(CONFIG_ENV_VAR_NAME))
  
          env = default
  
      return env
  
new_contents: # -*- coding: utf-8 -*-
  
  """
  byceps.util.system
  ~~~~~~~~~~~~~~~~~~
  
  :Copyright: 2006-2016 Jochen Kupperschmidt
  :License: Modified BSD, see LICENSE for details.
  """
  
  import os
  
  
  CONFIG_ENV_VAR_NAME = 'BYCEPS_CONFIG'
  
  
  def get_config_env_name_from_env():
      """Return the configuration environment name set via environment
      variable.
  
      Raise an exception if it isn't set.
      """
      env = os.environ.get(CONFIG_ENV_VAR_NAME)
  
      if not env:
          raise Exception(
              "No configuration environment was specified via the '{}' "
              "environment variable.".format(CONFIG_ENV_VAR_NAME))
  
      return env
  
subject: Remove default argument from function that reads the configuration name from the environment