[Samba] Crash on "samba-tool domain level raise --domain-level=2016 --forest-level=2016"

[Sebastian Neustein]

> the third instead failed:
>
>> samba-tool domain level raise --domain-level=2016 --forest-level=2016
>> ERROR(<class 'AttributeError'>): uncaught exception - 'NoneType' 
>> object has no attribute 'startswith'
>>   File "/usr/lib/python3/dist-packages/samba/netcmd/__init__.py", 
>> line 279, in _run
>>     return self.run(*args, **kwargs)
>>            ^^^^^^^^^^^^^^^^^^^^^^^^^
>>   File "/usr/lib/python3/dist-packages/samba/netcmd/domain/level.py", 
>> line 72, in run
>>     if subcommand == "raise" and not H.startswith("ldap"):
>>                                      ^^^^^^^^^^^^
> I tried with to take more information with gdb but failed:
>
> gdb --args /usr/bin/python3 /usr/bin/samba-tool domain level raise 
> --domain-level=2016 --forest-level=2016
>
>> (gdb) run
>> Starting program: /usr/bin/python3 /usr/bin/samba-tool domain level 
>> raise --domain-level=2016 --forest-level=2016
>> [Thread debugging using libthread_db enabled]
>> Using host libthread_db library 
>> "/lib/x86_64-linux-gnu/libthread_db.so.1".
>> ERROR(<class 'AttributeError'>): uncaught exception - 'NoneType' 
>> object has no attribute 'startswith'
>>   File "/usr/lib/python3/dist-packages/samba/netcmd/__init__.py", 
>> line 279, in _run
>>     return self.run(*args, **kwargs)
>>            ^^^^^^^^^^^^^^^^^^^^^^^^^
>>   File "/usr/lib/python3/dist-packages/samba/netcmd/domain/level.py", 
>> line 72, in run
>>     if subcommand == "raise" and not H.startswith("ldap"):
>>                                      ^^^^^^^^^^^^
>> [Inferior 1 (process 14932) exited with code 0377]
>> (gdb) bt full
>> No stack.
> If you need more information and I did it wrong  can you tell me what 
> I need to do please?
>
> Thanks for any reply and sorry for my bad english
Have you tried doing it step by step: first raise domain level and after 
that raising the forest level?