Please install the 'python3-apt' package but it's installed

[black-tul1p]

Describe the bug
After the successful installation of the program when I type in sudo katoolin3, the program says Please install the 'python-apt' package. I tried installing python3-apt but it's already installed. I also tried removing it and reinstalling it but I get the same message.

To Reproduce
Steps to reproduce the behavior:

1. git clone https://github.com/s-h-3-l-l/katoolin3 (I cloned the repository using terminal)
2. cd katoolin3/
3. chmod +x ./install.sh
4. sudo ./install.sh
   -> Executing: /tmp/apt-key-gpghome.vFtI16UEzG/gpg.1.sh -qq --keyserver pool.sks-keyservers.net --recv-keys ED444FF07D8D0BF6
   ->Successfully installed.
   ->Run it with 'sudo katoolin3'.
5. sudo katoolin3
   -> Please install the 'python-apt' package

Expected behavior
After it's installed, it should run katoolin 3 and allow me to download all the tools.