def default_properties_file
      # try the current directory
      file = File.expand_path(DEF_PROP_FILE_NM)
      return file if File.exists?(file)
      # try home
      home = ENV['HOME'] || ENV['USERPROFILE'] || '~'
      file = File.expand_path(DEF_PROP_FILE_NM, home)
      file if File.exists?(file)
    end
def default_properties_file
      # try the current directory
      file = File.expand_path(DEF_PROP_FILE_NM)
      return file if File.exists?(file)
      # try home
      home = ENV['HOME'] || ENV['USERPROFILE'] || '~'
      file = File.expand_path(DEF_PROP_FILE_NM, home)
      file if File.exists?(file)
    end
The default application properties file is determined as follows:
   * +./.catissue+, if it exists
   * +~/.catissue+, otherwise

 @return [String, nil] the default application properties file