On some machines (in my case, ubuntu 18.04 with 2.7.15+), I see
MGR_MODULE_ERROR Module 'devicehealth' has failed: Failed to import _strptime because the import lockis held by another thread.
Module 'devicehealth' has failed: Failed to import _strptime because the import lockis held by another thread.
This is apparently an issue with datetime on py2, see