`validators.hostname` lets long hostnames through if they contain periods

[Ddfulton]

Best explained with a very simple example:

>>> long_name_with_periods = 'kld8MXQh6YalMqKRbfs895gMjW5T4p2EwToPoCSThPHHbXgmXc.kld8MXQh6YalMqKRbfs895gMjW5T4p2EwToPoCSThPHHbXgmXc.kld8MXQh6YalMqKRbfs895gMjW5T4p2EwToPoCSThPHHbXgmXc.kld8MXQh6YalMqKRbfs895gMjW5T4p2EwToPoCSThPHHbXgmXc.kld8MXQh6YalMqKRbfs895gMjW5T4p2EwToPoCSThPHHbXgmXcab'

>>> assert len(lon_name_with_periods) > 255  # should be too long regardless of whether the dot-delimited "phrases" are <63chars

>>> assert validators.hostname(long_name_with_periods)  # Slips through the cracks

Maybe this has to do with the _simple_hostname_regex function?

[yozachar]

See: #407 (comment)