MAAS 2.5.1 – Failure to deploy CentOS 6 due to Curtin

I'm just trying to get a simple CentOS 6 deployment on one of my servers via MaaS, and every time I try to deploy CentOS 6, the deployment failed with this release of log failed:

Traceback (most recent call last):
File "/tmp/tmpnpq5oucc/target/curtin/curtin-hooks.py", line 393, in 
    main ()
File "/tmp/tmpnpq5oucc/target/curtin/curtin-hooks.py", line 376, in the main window
grub_root = get_grub_root (target)
File "/tmp/tmpnpq5oucc/target/curtin/curtin-hooks.py", line 208, in get_grub_root
returns regex.groups ()[0]
AttributeError: The object 'NoneType' there is no attribute 'groups & # 39;
Unexpected error while executing the command.
Order: ['/tmp/tmpnpq5oucc/target/curtin/curtin-hooks']
Exit code: 1
Reason: -
Stdout: & # 39;
Stderr: & # 39;
curtin: The installation failed with one exception: unexpected error while executing the command.
Order: ['curtin', 'curthooks']
Exit Code: 3
Reason: -
Stdout: Traceback (the most recent call last):
File "/tmp/tmpnpq5oucc/target/curtin/curtin-hooks.py", line 393, in 
        main ()
File "/tmp/tmpnpq5oucc/target/curtin/curtin-hooks.py", line 376, in the main window
grub_root = get_grub_root (target)
File "/tmp/tmpnpq5oucc/target/curtin/curtin-hooks.py", line 208, in get_grub_root
returns regex.groups ()[0]
    AttributeError: The object 'NoneType' there is no attribute 'groups & # 39;
Unexpected error while executing the command.
Order: ['/tmp/tmpnpq5oucc/target/curtin/curtin-hooks']
    Exit code: 1
Reason: -
Stdout: & # 39;
Stderr: & # 39;

Stderr: & # 39;

Something with Curtin and CentOS 6 seems not to be in perfect harmony. I can successfully deploy CentOS 7 without any problem, but for some reason, CentOS 6 gives me a lot of trouble and I do not find any similar problem online.