While cloudsw1-b1-codfw was rebooting for upgrade I noticed that the BFD check in Icinga failed. The SNMP poll of the device failed, as expected, but the check script did not handle it correctly:
```
Traceback (most recent call last):
File "/usr/lib/nagios/plugins/check_bfd.py", line 65, in <module>
main()
File "/usr/lib/nagios/plugins/check_bfd.py", line 37, in main
for index in snimpyManager.bfdSessState:
File "/usr/lib/python3/dist-packages/snimpy/manager.py", line 426, in __iter__
for k, _ in self.iteritems():
File "/usr/lib/python3/dist-packages/snimpy/manager.py", line 451, in iteritems
for noid, result in self.session.walk(oid):
File "/usr/lib/python3/dist-packages/snimpy/manager.py", line 127, in walk
return self.getorwalk("walkmore", *args)
File "/usr/lib/python3/dist-packages/snimpy/manager.py", line 112, in getorwalk
value = getattr(self._session, op)(*args)
File "/usr/lib/python3/dist-packages/snimpy/snmp.py", line 311, in walkmore
return self._op(self._cmdgen.bulkCmd, *args)
File "/usr/lib/python3/dist-packages/snimpy/snmp.py", line 267, in _op
raise SNMPException(str(errorIndication))
snimpy.snmp.SNMPException: No SNMP response received before timeout
```
Think we need to add exception handling for `snimpy.snmp.SNMPException`