Xmlto validation error when compiling gnuradio 3.6.2git

Ubuntu 10.04+gcc4.4.6+xmlto 0.0.23

Message
Linking CXX shared module _trellis.so
[ 82%] Built target _trellis
[ 83%] Built target pygen_gr_trellis_src_lib_35af8
[ 83%] Generating gr-trellis.html
xmlto: /home/highcheng/programs/gnuradio/gr-trellis/doc/gr-trellis.xml
does not validate (status 1)
xmlto: Fix document syntax or use --skip-validation option
warning: failed to load external entity
“/home/highcheng/programs/gnuradio/gr-trellis/doc/test_tcm.py.xml”
/home/highcheng/programs/gnuradio/gr-trellis/doc/gr-trellis.xml:481:
parser error : Failure to process entity test_tcm_listing
&test_tcm_listing;
^
/home/highcheng/programs/gnuradio/gr-trellis/doc/gr-trellis.xml:481:
parser error : Entity ‘test_tcm_listing’ not defined
&test_tcm_listing;
^
warning: failed to load external entity
“/home/highcheng/programs/gnuradio/gr-trellis/doc/test_viterbi_equalization1.py.xml”
/home/highcheng/programs/gnuradio/gr-trellis/doc/gr-trellis.xml:693:
parser error : Failure to process entity
test_viterbi_equalization1_listing
&test_viterbi_equalization1_listing;
^
/home/highcheng/programs/gnuradio/gr-trellis/doc/gr-trellis.xml:693:
parser error : Entity ‘test_viterbi_equalization1_listing’ not defined
&test_viterbi_equalization1_listing;
^