Implemented PEP 405 (Python virtual environments).

Tools/msi/msi.py

@@ -1122,6 +1122,7 @@ def add_files(db):
             lib.add_file("2to3.py", src="2to3")
             lib.add_file("pydoc3.py", src="pydoc3")
             lib.add_file("pysetup3.py", src="pysetup3")
+            lib.add_file("pyvenv.py", src="pyvenv")
             if have_tcl:
                 lib.start_component("pydocgui.pyw", tcltk, keyfile="pydocgui.pyw")
                 lib.add_file("pydocgui.pyw")

Tools/scripts/pyvenv

@@ -0,0 +1,11 @@
+#!/usr/bin/env python3
+if __name__ == '__main__':
+    import sys
+    rc = 1
+    try:
+        import venv
+        venv.main()
+        rc = 0
+    except Exception as e:
+        print('Error: %s' % e, file=sys.stderr)
+    sys.exit(rc)