Host OS: Debian Wheezy, fresh install
Poky version: tag dylan-9.0.1

This script uses file utility to determine type of compression. When file fails (non-zero return status) assumption is that compression is LZMA. It does not cover simple use case when file is just missing - not installed on host OS.

COMPRESSION=`($EXTRACTOR |file -) 2>/dev/null`
if echo $COMPRESSION |grep -iq gzip; then
        DECOMPRESSOR=gunzip
elif echo $COMPRESSION |grep -iq bzip2; then
        DECOMPRESSOR=bunzip2
elif echo $COMPRESSION |grep -iq xz; then
        DECOMPRESSOR=unxz
elif echo $COMPRESSION |grep -iq cpio; then
        DECOMPRESSOR=cat
else
        # Most versions of file don't support LZMA, therefore we assume
        # anything not detected is LZMA
        DECOMPRESSOR=`which unlzma 2>/dev/null`

In my case this script tried to unlzma rpmXYZ.tar.gz and failed saying something like 'unlzma: unknown format'. 
After installing file problem went away.

There is another script:
poky/meta/recipes-devtools/rpm/rpm/rpm2cpio
which does not use file, but awk to determine type of compression.

The solution would be either:
- add file as Yocto dependency to be installed on host OS
- change the script not to use file