diff -r 488ccbee6ee6 Lib/test/script_helper.py
--- a/Lib/test/script_helper.py	Thu Feb 13 10:54:32 2014 +0100
+++ b/Lib/test/script_helper.py	Thu Feb 13 11:26:29 2014 +0100
@@ -36,6 +36,11 @@ def _assert_python(expected_success, *ar
     # caller is responsible to pass the full environment.
     if env_vars.pop('__cleanenv', None):
         env = {}
+        if os.name == 'nt':
+            # Issue #20614: On Windows, CryptAcquireContext() fails with error
+            # 0x80090006 if the SYSTEMROOT environment variable is missing,
+            # probably because some DLL cannot be loaded.
+            env['SYSTEMROOT'] = os.environ['SYSTEMROOT']
     env.update(env_vars)
     cmd_line.extend(args)
     p = subprocess.Popen(cmd_line, stdin=subprocess.PIPE,