How to solve "OpenVPN requires super user privileges"
when I use "python3 crowbar.py -b openvpn -s 172.16.1.2/32 -p 1194 -m /root/WWW/vpn/client.ovpn -U /root/WWW/vpn/userlist -c 123456"
response: 2020-06-21 03:35:44 START 2020-06-21 03:35:44 Crowbar v0.4.1 OpenVPN requires super user privileges

You got this error due to the control in openvpn module. So, your user's SUDO_UID does not exist in environ.keys()'s output.
...
if not 'SUDO_UID' in os.environ.keys():
mess = "OpenVPN requires super user privileges"
...
You can check it by using env command in Kali. If you do not see SUDO_UID parameter, you can try it with sudo.
Note: You can see the difference from the picture below.

You got this error due to the control in openvpn module. So, your user's SUDO_UID does not exist in environ.keys()'s output.
... if not 'SUDO_UID' in os.environ.keys(): mess = "OpenVPN requires super user privileges" ...You can check it by using env command in Kali. If you do not see SUDO_UID parameter, you can try it with sudo.
Note: You can see the difference from the picture below.
but I AM root,Indeed, what should I do?

There are many solutions to solve it. But, two methods come to my mind quickly. 1. Run it with sudo
sudo python3 crowbar.py
2. You can change the line of the code
if not 'SUDO_UID' in os.environ.keys():
to
if 'SUDO_UID' in os.environ.keys():
There are many solutions to solve it. But, two methods come to my mind quickly. 1. Run it with sudo
sudo python3 crowbar.py2. You can change the line of the code
if not 'SUDO_UID' in os.environ.keys():to
if 'SUDO_UID' in os.environ.keys():
I use the second method, but there is to enter manually "Enter Auth Username"

There are many solutions to solve it. But, two methods come to my mind quickly. 1. Run it with sudo
sudo python3 crowbar.py2. You can change the line of the code
if not 'SUDO_UID' in os.environ.keys():to
if 'SUDO_UID' in os.environ.keys():I use the second method, but there is to enter manually "Enter Auth Username"
I think it is about your client.ovpn config file. I suggest you to remove auth-user-pass line in config and try again.
May I ask how to edite client.ovpn , is there a template?