title: E:The repository 'http://apt.postgresql.org/pub/repos/apt tessa-pgdg Release' does not have a Release file
body: <p>I have installed android studio on my linux mint 19.1 and after installation of it I restarted my PC. After restarting I couldn't see wi-fi sign in my machine.</p>
  
  <p>Enable wifi option is not showing. I opened driver manager and I got the above error. I have already tried <code>sudo apt-get update</code> and <code>sudo apt-get upgrade</code>. I also restarted my machine several times.</p>