This test occassionally fails on s390x and Power;
03:16:04 --- FAIL: TestExternalGraphDriver/pull (1.08s)
03:16:04 external_test.go:402: assertion failed: error is not nil: Error: No such image: busybox:latest
Most likely these failures are caused due to Docker Hub updating
the busybox:latest image, but not all architectures yet being
available.
Instead of using `:latest`, pull an image by digest, so that
the test doesn't depend on Docker Hub having all architectures
available for `:latest`.
I selected the same digest as is currently used as "frozen image"
in the Dockerfile.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
352db26d5f