bpo-32409 Fix regression in activate.bat on international Windows (GH-10295)

Handle Unicode contents on localized Windows systems when activating a
virtualenv. activate.bat currently breaks on German Windows systems as chcp does
not return a plain number as on English systems, but appends a dot at the end
(for example "Aktive Codepage: 850." instead of "Active Codepage: 850). The
dependency to chcp.com is removed and ctypes is used to get, set and restore the
console ouput codepage. The codepage for console input is not changed.

We can't use __VENV_PYTHON__ to find python.exe since it's UTF-8. CMD decodes
the script using the console output codepage.

Author: samstagern

Lib/venv/scripts/nt/activate.bat

@@ -1,11 +1,10 @@
 @echo off
 
-rem This file is UTF-8 encoded, so we need to update the current code page while executing it
-for /f "tokens=2 delims=:" %%a in ('"%SystemRoot%\System32\chcp.com"') do (
-    set "_OLD_CODEPAGE=%%a"
-)
+rem This file is UTF-8 encoded, so we need to update the current code page while executing it.
+for /f %%a in ('%~dp0python.exe -Ic "import ctypes; print(ctypes.windll.kernel32.GetConsoleOutputCP())"') do (set "_OLD_CODEPAGE=%%a")
+
 if defined _OLD_CODEPAGE (
-    "%SystemRoot%\System32\chcp.com" 65001 > nul
+    %~dp0python.exe -Ic "import ctypes; ctypes.windll.kernel32.SetConsoleOutputCP(65001)"
 )
 
 set "VIRTUAL_ENV=__VENV_DIR__"
@@ -40,6 +39,6 @@ set "PATH=%VIRTUAL_ENV%\__VENV_BIN_NAME__;%PATH%"
 
 :END
 if defined _OLD_CODEPAGE (
-    "%SystemRoot%\System32\chcp.com" %_OLD_CODEPAGE% > nul
+    %~dp0python.exe -Ic "import ctypes; ctypes.windll.kernel32.SetConsoleOutputCP(%_OLD_CODEPAGE%)"
     set "_OLD_CODEPAGE="
 )

Misc/NEWS.d/next/Library/2018-11-02-12-01-00.bpo-32409.MFRX2Q.rst

@@ -0,0 +1,2 @@
+Fixed implementation of :file:`activate.bat` to handle Unicode contents on
+localized Windows systems (eg. German). Patch by Martin Bijl.