[libvirt] build failed with warning " failed to load external entity "api.html.tmp"

I got the latest code and build it with following error on Ubuntu 11.10: ...... make all-am make[3]: Entering directory `/home/wayne/workspace/project/libvirt/tools' CC virsh-console.o CC virsh-virsh.o CCLD virsh GEN virt-xml-validate GEN virt-pki-validate make[3]: Leaving directory `/home/wayne/workspace/project/libvirt/tools' make[2]: Leaving directory `/home/wayne/workspace/project/libvirt/tools' Making all in docs make[2]: Entering directory `/home/wayne/workspace/project/libvirt/docs' Validating api.html warning: failed to load external entity "api.html.tmp" make[2]: *** [api.html] Error 1 make[2]: Leaving directory `/home/wayne/workspace/project/libvirt/docs' make[1]: *** [all-recursive] Error 1 make[1]: Leaving directory `/home/wayne/workspace/project/libvirt' make: *** [all] Error 2 I think some dependent packages are missed on my build environment. But the error information doesn't show some hint. Does anyone know the reason? Thanks. Wenyi Gao