bpo-46720: Add support for path-like objects to multiprocessing.set_executable for Windows to be on a par with Unix-like systems

Lib/multiprocessing/spawn.py

@@ -43,7 +43,10 @@ def set_executable(exe):
     _python_exe = exe
 
 def get_executable():
-    return _python_exe
+    if sys.platform == 'win32':
+        return os.fsdecode(_python_exe)
+    else:
+        return os.fsencode(_python_exe)
 
 #
 #
@@ -86,7 +89,8 @@ def get_command_line(**kwds):
         prog = 'from multiprocessing.spawn import spawn_main; spawn_main(%s)'
         prog %= ', '.join('%s=%r' % item for item in kwds.items())
         opts = util._args_from_interpreter_flags()
-        return [_python_exe] + opts + ['-c', prog, '--multiprocessing-fork']
+        exe = get_executable()
+        return [exe] + opts + ['-c', prog, '--multiprocessing-fork']
 
 
 def spawn_main(pipe_handle, parent_pid=None, tracker_fd=None):

Lib/multiprocessing/util.py

@@ -450,7 +450,7 @@ def spawnv_passfds(path, args, passfds):
     errpipe_read, errpipe_write = os.pipe()
     try:
         return _posixsubprocess.fork_exec(
-            args, [os.fsencode(path)], True, passfds, None, None,
+            args, [path], True, passfds, None, None,
             -1, -1, -1, -1, -1, -1, errpipe_read, errpipe_write,
             False, False, None, None, None, -1, None)
     finally: