class HttpParser::Instance

def error
    error = (self[:error_upgrade] & 0b1111111)
    return nil if error == 0
    err = ::HttpParser.err_name(error)[4..-1] # HPE_ is at the start of all these errors
    klass = ERRORS[err.to_sym]
    err = "#{::HttpParser.err_desc(error)} (#{err})"
    return klass.nil? ? Error::UNKNOWN.new(err) : klass.new(err)
end