text: ##############################################################################
  #
  # Copyright (c) 2006 Zope Foundation and Contributors.
  #
  # This software is subject to the provisions of the Zope Public License,
  # Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
  # THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
  # WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  # WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
  # FOR A PARTICULAR PURPOSE.
  #
  ##############################################################################
  """Error related things.
  """
  try:
      from html import escape
  except ImportError:     # pragma: NO COVER
      from cgi import escape
  
  from zope.component import adapter
  from zope.interface import implementer
  from zope.interface import Invalid
  from zope.i18n import Message
  from zope.i18n import translate
  
  from zope.publisher.interfaces.browser import IBrowserRequest
  from zope.publisher.browser import BrowserPage
  from zope.formlib.interfaces import IWidgetInputErrorView
  from zope.formlib.interfaces import IInvalidCSRFTokenError
  
  
  @implementer(IWidgetInputErrorView)
  @adapter(Invalid, IBrowserRequest)
  class InvalidErrorView(object):
      """Display a validation error as a snippet of text."""
  
      def __init__(self, context, request):
          self.context = context
          self.request = request
  
      def snippet(self):
          """Convert a widget input error to an html snippet
  
          >>> from zope.interface.exceptions import Invalid
          >>> error = Invalid("You made an error!")
          >>> InvalidErrorView(error, None).snippet()
          u'<span class="error">You made an error!</span>'
          """
          msg = self.context.args[0]
          if isinstance(msg, Message):
              msg = translate(msg, context=self.request)
          return u'<span class="error">%s</span>' % escape(msg)
  
  
  @adapter(IInvalidCSRFTokenError, IBrowserRequest)
  class InvalidCSRFTokenErrorView(BrowserPage):
  
      def update(self):
          self.request.response.setStatus(403)
          self.request.response.setHeader(
              'Expires', 'Jan, 1 Jan 1970 00:00:00 GMT')
          self.request.response.setHeader(
              'Cache-Control', 'no-store, no-cache, must-revalidate')
          self.request.response.setHeader(
              'Pragma', 'no-cache')
  
      def render(self):
          msg = self.context.args[0]
          if isinstance(msg, Message):
              msg = translate(msg, context=self.request)
          return escape(msg)
  
      def __call__(self):
          self.update()
          return self.render()
  