w9xpopen.exe is a utility program shipped with Python <3.4
(https://bugs.python.org/issue14470 tracked its removal).
The program was used by subprocess to wrap invoked processes
on Windows 95 and 98 or when command.com was used in order to
work around a redirect bug.
The workaround is only used on ancient Windows versions -
versions that we shouldn't see in 2019.
While Python 2.7's subprocess module still references
w9xpopen.exe, not shipping it shouldn't matter unless we're
running an ancient version of Windows. Python will raise
an exception if w9xpopen.exe can't be found.
It's highly unlikely anyone is using current Mercurial releases
on these ancient Windows versions. So remove w9xpopen.exe
from the Inno installer.
The 32-bit Windows Inno installers no longer distribute w9xpopen.exe. This should only impact people running Mercurial on Windows 95, 98, or ME.