ReadError, "not a bzip2 file"

[itzel]

Hello!!
In using tarfile to group thousands of small files from a directory and
then compress it. I already compress a group of files in my pc, but I
need do it in a server and I'm testing the same procedure, but it
doesn't work . A "ReadError" appear: "not a bzip2 file". I'm using this
script:

import os
import tarfile

dstfolder = '/somepath/to/output'    ## server
fileorfoldertobackup = '/home/username'  ##  server
dst = '%s.tar.bz2' % os.path.join(dstfolder,
os.path.basename(fileorfoldertobackup))
out = tarfile.TarFile.open(dst, 'w:bz2')
out.add(fileorfoldertobackup,
arcname=os.path.basename(fileorfoldertobackup))
out.close()

What I´m doing wrong? Is necesary install a python version into the
server??

Thanks!!