DeepSpeed

66fb9241 - launcher/launcher_helper.py: fix PMI name and add EnvironmentError (#5025)

launcher/launcher_helper.py: fix PMI name and add EnvironmentError (#5025) Hi, for my last PR https://github.com/microsoft/DeepSpeed/pull/4699 about launcher_helper, it mistakenly used two "PMIX". In this PR I corrected them to be "PMIX" and "PMI". And I also added _EnvironmentError_ to make sure env not get _NONE_ type, otherwise it would trigger env setting error.