This package has what appears to be a flaky self-test, which causes
testing migration blocking of golang-testify right now.

https://ci.debian.net/packages/g/golang-github-insomniacslk-dhcp/testing/arm64/70979203/#L1969

/Simon

 89s === RUN   TestSendAndReadUntil/discard_wrong_XID
 89s panic: connection refused
 89s
 89s goroutine 26 [running]:
 89s github.com/insomniacslk/dhcp/dhcpv6/nclient6.(*handler).handle(0x71bbe5916c80, {0x675b80, 0x71bbe592a4c8}, {0x0, 0x0}, {0x6763a8?, 0x71bbe592e9a0})
 89s 	/tmp/autopkgtest-lxc.4l4waoh5/downtmp/autopkgtest_tmp/_build/src/github.com/insomniacslk/dhcp/dhcpv6/nclient6/client_test.go:46 +0x290
 89s created by github.com/insomniacslk/dhcp/dhcpv6/server6.(*Server).Serve in goroutine 25
 89s 	/tmp/autopkgtest-lxc.4l4waoh5/downtmp/autopkgtest_tmp/_build/src/github.com/insomniacslk/dhcp/dhcpv6/server6/server.go:97 +0x2ec
 89s FAIL	github.com/insomniacslk/dhcp/dhcpv6/nclient6	0.011s