old_contents: 
  store_contents = {}
  store_structure = {}
  
  store_contents['_default_errors'] = [
          'src/_errors/index.recipe',
          ]
  
  store_structure['recipes'] = {}
  store_structure['bags'] = {}
  
  store_structure['recipes']['_errors'] = {
          'desc': 'Pretty Errors Error Tiddlers',
          'recipe': [
              ('_default_errors', ''),
              ('_errors', ''),
              ],
          'policy': {
              'read': [],
              'write': ['R:ADMIN'],
              'manage': ['R:ADMIN'],
              'delete': ['R:ADMIN'],
              'owner': 'administractor',
              'write': ['R:ADMIN'],
              },
          }
  
  store_structure['bags']['_default_errors'] = {
          'desc': 'Default error tiddlers for Pretty Errors',
          'policy': {
              'read': [],
              'write': ['NONE'],
              'create': ['NONE'],
              'delete': ['NONE'],
              'manage': ['NONE'],
              'accept': ['NONE'],
              'owner': 'administrator',
              },
          }
  
  store_structure['bags']['_errors'] = {
          'desc': 'Override error tiddlers for Pretty Errors',
          'policy': {
              'read': [],
              'write': ['R:ADMIN'],
              'create': ['R:ADMIN'],
              'delete': ['R:ADMIN'],
              'manage': ['R:ADMIN'],
              'accept': ['NONE'],
              'owner': 'administrator',
              },
          }
  
  instance_config = {
          'system_plugins': ['tiddlywebplugins.prettyerror'],
          }
  
new_contents: """
  Establish the data structures representing the bags and recipes needed
  by this plugin.
  """
  
  store_contents = {}
  store_structure = {}
  
  store_contents['_default_errors'] = [
          'src/_errors/index.recipe',
          ]
  
  store_structure['recipes'] = {}
  store_structure['bags'] = {}
  
  store_structure['recipes']['_errors'] = {
          'desc': 'Pretty Errors Error Tiddlers',
          'recipe': [
              ('_default_errors', ''),
              ('_errors', ''),
              ],
          'policy': {
              'read': [],
              'write': ['R:ADMIN'],
              'manage': ['R:ADMIN'],
              'delete': ['R:ADMIN'],
              'owner': 'administractor',
              'create': ['R:ADMIN'],
              },
          }
  
  store_structure['bags']['_default_errors'] = {
          'desc': 'Default error tiddlers for Pretty Errors',
          'policy': {
              'read': [],
              'write': ['NONE'],
              'create': ['NONE'],
              'delete': ['NONE'],
              'manage': ['NONE'],
              'accept': ['NONE'],
              'owner': 'administrator',
              },
          }
  
  store_structure['bags']['_errors'] = {
          'desc': 'Override error tiddlers for Pretty Errors',
          'policy': {
              'read': [],
              'write': ['R:ADMIN'],
              'create': ['R:ADMIN'],
              'delete': ['R:ADMIN'],
              'manage': ['R:ADMIN'],
              'accept': ['NONE'],
              'owner': 'administrator',
              },
          }
  
  instance_config = {
          'system_plugins': ['tiddlywebplugins.prettyerror'],
          }
  
subject: Correct set policy on bag.