bpo-41627: Distinguish 32 and 64-bit user site packages on Windows (GH-22098)

Also fixes the error message returned when sysconfig fails to interpolate a variable correctly.
diff --git a/Lib/site.py b/Lib/site.py
index 8979365..4c09577 100644
--- a/Lib/site.py
+++ b/Lib/site.py
@@ -274,7 +274,8 @@
     version = sys.version_info
 
     if os.name == 'nt':
-        return f'{userbase}\\Python{version[0]}{version[1]}\\site-packages'
+        ver_nodot = sys.winver.replace('.', '')
+        return f'{userbase}\\Python{ver_nodot}\\site-packages'
 
     if sys.platform == 'darwin' and sys._framework:
         return f'{userbase}/lib/python/site-packages'