Resurrect Balint's fix from

lp:~rbalint/livecd-rootfs/livecd-rootfs-autopkgtest-fix to wrap kpartx
and trap spurious errors, since the problem is still being seen
intermittently on i386 despite us calling sync before kpartx. (LP: #1684090)

debian/changelog

@@ -1,5 +1,9 @@
 livecd-rootfs (2.441.3) UNRELEASED; urgency=medium
 
+  * Resurrect Balint's fix from
+    lp:~rbalint/livecd-rootfs/livecd-rootfs-autopkgtest-fix to wrap kpartx
+    and trap spurious errors, since the problem is still being seen
+    intermittently on i386 despite us calling sync before kpartx. (LP: #1684090)
   * Mark autopkgtests isolation-machine since debootstrap won't work in a
     container.
 

live-build/functions

@@ -11,9 +11,22 @@ backing_img=
 apt-get -qqy install dosfstools gdisk
 
 clean_loops() {
+    local kpartx_ret
+    local kpartx_stdout
 
     if [ -n "${backing_img}" ]; then
-        kpartx -v -d "${backing_img}"
+        # sync before removing loop to avoid "Device or resource busy" errors
+        sync
+        kpartx_ret=""
+        kpartx_stdout=$(kpartx -v -d "${backing_img}") || kpartx_ret=$?
+        echo "$kpartx_stdout"
+        if [ -n "$kpartx_ret" ]; then
+            if echo "$kpartx_stdout" | grep -q "loop deleted: "; then
+                echo "Suppressing kpartx returning error (#860894)"
+            else
+                exit $kpartx_ret
+            fi
+        fi
         unset backing_img
     fi