A DDG search (choose your favorite web search engine) suggests a handful of things:
. Shorten your %PATH% variable so it is ridiculously short.
. Make sure there is only the SYSTEM PATH defined, remove any user defined PATH variable.
. Run cmd.exe as administrator and start the installer from there.
. Review the install.log for other errors.
I have not personally experienced this problem, just mentioning what others have experienced over the years...
Finally i ignored the error and the installation succeeded.
I am still interested what caused the installer to report this error on Windows 10 Pro Version 1703.