autopkgtest fails in hirsute on s390x

[Balint Reczey]

https://autopkgtest.ubuntu.com/packages/c/casync/hirsute/s390x

https://objectstorage.prodstack4-5.canonical.com/v1/AUTH_77e2ada1e7a84929a74ba3b87153c0ac/autopkgtest-hirsute/hirsute/s390x/c/casync/20210330_165933_9e945@/log.gz

...
Total extract time: 69ms
+ /tmp/autopkgtest.wLcpm0/build.Rls/src/obj-s390x-linux-gnu/test-calc-digest sha512-256 /var/tmp/test-casync.7979/blob2
+ /tmp/autopkgtest.wLcpm0/build.Rls/src/obj-s390x-linux-gnu/test-calc-digest sha512-256 /var/tmp/test-casync.7979/blob3
+ diff -q /var/tmp/test-casync.7979/test.digest /var/tmp/test-casync.7979/extract.digest
+ diff -q /var/tmp/test-casync.7979/test.digest /var/tmp/test-casync.7979/extract2.digest
+ '[' 0 = 0 ']'
+ modprobe nbd
+ '[' -e /dev/nbd0 -a 1 = 1 ']'
++ /tmp/autopkgtest.wLcpm0/build.Rls/src/obj-s390x-linux-gnu/notify-wait /tmp/autopkgtest.wLcpm0/build.Rls/src/obj-s390x-linux-gnu/casync -v --digest=sha512-256 mkdev /var/tmp/test-casync.7979/test.caibx /var/tmp/test-casync.7979/test-node
+ MKDEV_PID=6616
+ /tmp/autopkgtest.wLcpm0/build.Rls/src/obj-s390x-linux-gnu/test-calc-digest sha512-256
+ dd if=/var/tmp/test-casync.7979/test-node bs=102400 count=80
0+0 records in
0+0 records out
0 bytes copied, 6.1388e-05 s, 0.0 kB/s
+ diff -q /var/tmp/test-casync.7979/test.digest /var/tmp/test-casync.7979/mkdev.digest
-------

Summary of Failures:

 5/22 test-nbd.sh FAIL 1.02s (exit status 1)

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