Check PowerShell execution policy (#1114)

tools/nni_cmd/launcher.py

@@ -343,6 +343,13 @@ def set_experiment(experiment_config, mode, port, config_file_name):
 def launch_experiment(args, experiment_config, mode, config_file_name, experiment_id=None):
     '''follow steps to start rest server and start experiment'''
     nni_config = Config(config_file_name)
+    # check execution policy in powershell
+    if sys.platform == 'win32':
+        execution_policy = check_output(['powershell.exe','Get-ExecutionPolicy']).decode('ascii').strip()
+        if execution_policy == 'Restricted':
+            print_error('PowerShell execution policy error, please run PowerShell as administrator with this command first:\r\n'\
+                + '\'Set-ExecutionPolicy -ExecutionPolicy Unrestricted\'')
+            exit(1)
     # check packages for tuner
     package_name, module_name = None, None
     if experiment_config.get('tuner') and experiment_config['tuner'].get('builtinTunerName'):