I had troubles starting the SNMP service with VyOS 1.2-rolling-201910110117.
After some debugging I found that the SNMP configuration generator
/usr/libexec/vyos/conf_mode/snmp.py
added the following arguments to the snmpd.service file
-LSed -u snmp -g snmp -I -ipCidrRouteTable, inetCidrRouteTable -p /run/snmpd.pid
After removing the space character between the comma and inetCidrRouteTable as in
-LSed -u snmp -g snmp -I -ipCidrRouteTable,inetCidrRouteTable -p /run/snmpd.pid
the SNMPD service started successfully.