Fixes issue #20954: _args_from_interpreter_flags used by multiprocessing

and some tests no longer behaves incorrectly in the presence of the
PYTHONHASHSEED environment variable.

Lib/subprocess.py

@@ -498,7 +498,6 @@ def _args_from_interpreter_flags():
         'ignore_environment': 'E',
         'verbose': 'v',
         'bytes_warning': 'b',
-        'hash_randomization': 'R',
         'py3k_warning': '3',
     }
     args = []
@@ -506,6 +505,8 @@ def _args_from_interpreter_flags():
         v = getattr(sys.flags, flag)
         if v > 0:
             args.append('-' + opt * v)
+    if getattr(sys.flags, 'hash_randomization') != 0:
+        args.append('-R')
     for opt in sys.warnoptions:
         args.append('-W' + opt)
     return args

Misc/NEWS

@@ -22,6 +22,10 @@ Core and Builtins
 Library
 -------
 
+- Issue #20954: _args_from_interpreter_flags used by multiprocessing and some
+  tests no longer behaves incorrectly in the presence of the PYTHONHASHSEED
+  environment variable.
+
 - Issue #14285: When executing a package with the "python -m package" option,
   and package initialization raises ImportError, a proper traceback is now
   reported.