Return a text string describing the context

def FormatContext(self):
    """Return a text string describing the context"""
    text = ''
    if hasattr(self, 'feed_name'):
      text += "In feed '%s': " % self.feed_name
    if hasattr(self, 'file_name'):
      text += self.file_name
    if hasattr(self, 'row_num'):
      text += ":%i" % self.row_num
    if hasattr(self, 'column_name'):
      text += " column %s" % self.column_name
    return text