upgrade samba 4 alpha9 to samba 4 alpha 11-error

[hesam mohamadian]

hi i installed samba4 alpha 9  and i want to upgrade to samba4 alpha11 , i
get samba4 alpha11 from git and for upgrading i do this :
./scripting/bin/
>
> upgradeprovision --full -s
> /usr/local/backupprovision/etc/smb.conf
>
> Traceback (most recent call last):
>   File "./scripting/bin/upgradeprovision", line 36, in<module>
>     import ldb
> ImportError: No module named ldb
>
*my git version is : 1.6.3.3
my os is : ubuntu : 9.10 server
my python version :  2.6.4
*
can you help me please ?