When using the python sandbox client together with the example/python-runtime-template that uses gvisor (runsc) since it does not support kubectl port forwarding (planned to be supported later):

E1113 12:13:55.326947 1362781 portforward.go:424] "Unhandled Error" err="an error occurred forwarding 8000 -> 8888: error forwarding port 8888 to pod 08a55c7e040cff8ffbcab832623815bc6c00e3563beb1d5282abde2e5b5a63ad, uid : failed to execute portforward in network namespace "/var/run/netns/cni-f9e07cfe-3e9e-b41e-3cb7-a5aab2d16661": failed to connect to localhost:8888 inside namespace