Trouble in installing O2

Dear Experts,

I am facing the following errors for pre-installing the O2, via Doctor, on Ubuntu 16.04

ERROR: Package Python-system is a system requirement and cannot be found.
ERROR: This is due to the fact that the following script fails:
ERROR: python3 -c ‘import sys; import sqlite3; sys.exit(1 if sys.version_info < (3,6) else 0)’ && pip3 help
ERROR: with the following output:
ERROR: Python-system:
ERROR: Python 3.6 is missing from your system. We need the python3 and pip3 executables in the PATH.
ERROR: It can be installed with:
ERROR: * On Ubuntu: sudo apt-get install python3 python3-pip python3-tk
ERROR: * On macOS: brew install python3
SUCCESS: Package libpng will be picked up from the system.

Although all python3 packages have been installed and I am also trying via changing the environment in bash file from python to python3,

Any help please.

Kind regards,

Do you have python3-pip installed?

Dear Giulio,

Thanks for your reply. Yes python3-pip has been installed.

Could you try applying to alidist?

Dear Giulio,

Thanks. I have opened the link and not finding what to do. Could you please describe in steps.