"growpart" spits out a non-fatal error message on systems where
partx does not support the "--help" option.

# /usr/bin/growpart /dev/vda 1
partx: unrecognized option '--help'
unknown option

This is with:

# rpm -qf /usr/bin/growpart
cloud-utils-0.27-3.el6.noarch

A trivial patch quiesces the script:

--- /usr/bin/growpart   2013-05-23 15:26:15.585033492 +0200
+++ /usr/bin/growpart-  2013-05-23 15:26:41.795992384 +0200
@@ -448,7 +448,7 @@
        fi
 
        if command -v partx >/dev/null 2>&1; then
-               partx --help 2>/dev/null | grep -q -- --update || {
+               partx --help | grep -q -- --update || {
                        reason="partx has no '--update' flag in usage."
                        found="off"
                }