The preflight page began refusing to continue while any check was failing, which
is right for something the operator must go and fix. HttpPlatformHandler was
marked FAIL when absent - so on a server without it the wizard stopped dead,
telling the operator the server was not ready, over a module the bundle carries
and stage 4 installs a few pages later. The only way forward was to go and
install by hand the exact thing the installer was about to install.
It is now INFO: reported, not blocking, matching how URL Rewrite is already
handled. Nothing the installer SUPPLIES may block the wizard, and
tests/test_installer_defaults.py now fails if that rule is broken again.
The site-port conflict check is downgraded from FAIL to WARN for the same class
of reason: it runs before the operator reaches the Address page, so it tests the
DEFAULT port rather than the one they intend to use, and blocking refuses an
install over a conflict the very next page lets them resolve.
Genuine blockers are unchanged - no IIS, no WebAdministration, wrong Windows
edition or architecture, no disk, and the MySQL 5.6 index flags. Those the
operator really does have to fix first.