Installation failed by "No module named site" message

[jeffwji]

I'm trying to install rPython on Windows 7, failed by "No module named site". My environment configuration is:

Python 3.6.3 is installed under "C:\Program Files\Python\Python36" which is default location.

Rtools is installed under C:\Rtools, with mingw_64 (and 32 bit version) underneath.

PATH is set as "%PATH%;C:\Rtools\bin;C:\Rtools\mingw_64\bin"

configure.win file content is:

#!/bin/sh

echo 'PKG_LIBS=-LC:/Program Files/Python/Python36/libs -lpython36'  > src/makevars.win
echo 'PKG_CFLAGS=-I"C:/Program Files/Python/Python36/include"'     >> src/makevars.win

R version is 3.4.1

Install command:

install.packages("devtools")
library(devtools)
install("C:/DevApps/R/rPython")

Detail error message:

Installing rPython
"C:/PROGRA~1/R/R-34~1.0/bin/x64/R" --no-site-file --no-environ --no-save --no-restore --quiet CMD INSTALL "C:/DevApps/R/rPython"  \
  --library="C:/Users/326487162/Documents/R/win-library/3.4" --install-tests 

* installing *source* package 'rPython' ...
** libs
Warning: this package has a non-empty 'configure.win' file,
so building only the main architecture

make: Nothing to be done for `all'.
installing to C:/Users/326487162/Documents/R/win-library/3.4/rPython/libs/x64
** R
** inst
** preparing package for lazy loading
Warning: package 'RJSONIO' was built under R version 3.4.1
** help
*** installing help indices
** building package indices
** testing if installed package can be loaded
Warning: package 'RJSONIO' was built under R version 3.4.1
ImportError: No module named site
ERROR: loading failed
* removing 'C:/Users/326487162/Documents/R/win-library/3.4/rPython'
Error: Command failed (1)

The output information is not very clear what it was trying to import? and why it was failed. How can I fix it?