Add missing sys imports (#343)

Author: spilkey-cisco

sonic_platform_base/fan_drawer_base.py

@@ -5,6 +5,7 @@
     to interact with a fan drawer module in SONiC
 """
 
+import sys
 from . import device_base
 
 

sonic_platform_base/psu_base.py

@@ -5,6 +5,7 @@
     to interact with a power supply unit (PSU) in SONiC
 """
 
+import sys
 from . import device_base