slaprunner: Export (rsync) silence rsync warning

When a file is removed while rsync is running (after build the list and before transfer the file), rsync fail with the follow message:

     rsync warning: some files vanished before they could be transferred

Long back rafael proped a solution here 387d3b7e
But it seems like adding --ignore-missing-args dont really help but just ignore the files given in args and are counldn't be found anymore.

/reviewed-on nexedi/slapos!225

software/slaprunner/buildout.hash.cfg

@@ -31,7 +31,7 @@ md5sum = 5cfa49bcf20612844e1c50a85740d0b3
 
 [template-runner-export-script]
 filename = template/runner-export.sh.jinja2
-md5sum = 94c0eddb2af3290942f64e04f95a707c
+md5sum = 78b2454951e6dbe124612eafebcf5690
 
 [instance-runner-export]
 filename = instance-runner-export.cfg.in

software/slaprunner/template/runner-export.sh.jinja2

@@ -19,9 +19,21 @@ etc_directory='{{ directory["etc"] }}'
 tmp_directory='{{ directory["tmp"] }}'
 
 rsync () {
+  # Workaround for bug https://bugzilla.samba.org/show_bug.cgi?id=3653
+  IGNOREEXIT=24
+  IGNOREOUT='^(file has vanished: |rsync warning: some files vanished before they could be transferred)'
+  set -o pipefail
+
   set -x
-  '{{ rsync_binary }}' -rlptgov --stats --safe-links --ignore-missing-args --delete --delete-excluded "$@"
+  '{{ rsync_binary }}' -rlptgov --stats --safe-links --ignore-missing-args --delete --delete-excluded "$@" 2>1 | (egrep -v "$IGNOREOUT" || true)
   set +x
+
+  ret=$?
+  if [[ $ret == $IGNOREEXIT ]]; then
+    ret=0
+  fi
+
+  exit $ret
 }
 
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