gh-101283: Fix use of unbound variable (GH-101712)

Author: zooba

Lib/subprocess.py

@@ -1494,6 +1494,8 @@ def _execute_child(self, args, executable, preexec_fn, close_fds,
                             raise FileNotFoundError('shell not found: neither %ComSpec% nor %SystemRoot% is set')
                     if os.path.isabs(comspec):
                         executable = comspec
+                else:
+                    comspec = executable
 
                 args = '{} /c "{}"'.format (comspec, args)