yanger: Handle the case when a container interface can not be found

Due to #902 (which has not been root caused at this time), podman may
indicate the existance of an interface that yanger is not able to
locate in any namespace. Therefore, make sure that we verify that the
interface was actually found before trying to create the operational
data for it.

src/statd/python/yanger/ietf_interfaces/container.py

@@ -16,6 +16,8 @@ def find_interface(cifname):
                 ipaddrs = common.ipaddrs(ifname=iplink["ifname"], netns=ns["name"])
                 return (iplink, next(iter(ipaddrs.values())))
 
+    return (None, None)
+
 
 def podman_interfaces():
     interfaces = {}
@@ -31,6 +33,7 @@ def podman_interfaces():
 
     return interfaces
 
+
 def interfaces(ifname):
     interfaces = []
 
@@ -39,6 +42,9 @@ def interfaces(ifname):
             continue
 
         iplink, ipaddr = find_interface(cifname)
+        if not (iplink and ipaddr):
+            continue
+
         interface = link.interface_common(iplink, ipaddr)
 
         # The original interface name is stored in ifalias by podman -