DeprecationWarning: In future versions of Waitress clear_untrusted_proxy_headers will be set to True by default. You may opt-out by setting this value to False, or opt-in explicitly by setting this to True.
Source: https://docs.pylonsproject.org/projects/waitress/en/stable/arguments.html?highlight=clear_untrusted_proxy_headers
> This tells Waitress to remove any untrusted proxy headers ("Forwarded",
> "X-Forwared-For", "X-Forwarded-By", "X-Forwarded-Host", "X-Forwarded-Port",
> "X-Forwarded-Proto") not explicitly allowed by trusted_proxy_headers.
According to grep we don't use any of those headers so let's turn it on for
security reasons.