Log Message:
Update security/py-certbot to 0.16.0.

Added
- A plugin for performing DNS challenges using dynamic DNS updates as
  defined in RFC 2316 (available separately).
- Plugins for performing DNS challenges for the providers DNS Made
  Easy and LuaDNS (available separately).
- Support for performing TLS-SNI-01 challenges when using the manual
  plugin.
- Automatic detection of Arch Linux in the Apache plugin providing
  better default settings for the plugin.

Changed
- The text of the interactive question about whether a redirect from
  HTTP to HTTPS should be added by Certbot has been rewritten to
  better explain the choices to the user.
- Simplified HTTP challenge instructions in the manual plugin.

Fixed
- Problems performing a dry run when using the Nginx plugin have been
  fixed.
- Resolved an issue where certbot-dns-digitalocean's test suite would
  sometimes fail when ran using Python 3.
- On some systems, previous versions of certbot-auto would error out
  with a message about a missing hash for setuptools.
- A bug where Certbot would sometimes not print a space at the end of
  an interactive prompt has been resolved.
- Nonfatal tracebacks are no longer shown in rare cases where Certbot
  encounters an exception trying to close its TCP connection with the
  ACME server.