Unable to locate package apt_pkg

Question

I opened Ubuntu 16.04 after more than 2 months and now I receive an error to install any package (I tried to install redshift package(night mode)).

ERROR E: Unable to locate package apt_pkg

I tried to update Ubuntu, then I received errors:

W: The repository 'http://ppa.launchpad.net/jonathonf/python-3.6/ubuntu xenial Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Failed to fetch http://ppa.launchpad.net/jonathonf/python-3.6/ubuntu/dists/xenial/main/binary-amd64/Packages  404  Not Found [IP: 91.189.95.83 80]
E: Some index files failed to download. They have been ignored, or old ones used instead.

Another issue is terminal isn't opening from search bar, I am forced to right-click on desktop and select to open it. Software & updates and even software updater programs are not opening (It's like opening for 1 sec and closing).

I tried to reinstall gnome-software. After uninstalling it, I get an error:

E: Package 'gnome-software' has no installation candidate

Solution

since @jonathonf recently removed most of his PPAs from public access, you cannot use it publicly anymore.

so you need to remove this by

add-apt-repository -r ppa:jonathonf/python-3.6

Note, if you need Python 3.6, an alternative to the jonathonf PPA is the deadsnakes PPA. Use sudo add-apt-repository ppa:deadsnakes/ppa, cf. How do I install Python 3.6 using apt-get?

Comments

[AGVG]

I get an error trying this : ModuleNotFoundError: No module named 'apt_pkg' @Jim

[Jim]

@GOUTHAMA.G.V. that's another issue, maybe this can help askubuntu.com/a/1063420/838210

[AGVG]

Tried all of them, none of them worked. The thing is I didn't install python at all. I get the following error: Reinstallation of python3-apt is not possible, it cannot be downloaded.