BUG #15586: Failed to start PostgreSQL Cluster 10-main

The following bug has been logged on the website:

Bug reference:      15586
Logged by:          Noyal Claiton
Email address:      modelmiscreants@gmail.com
PostgreSQL version: 10.6
Operating system:   Ubuntu 18.04
Description:

Team,

If I'm addressing this email to inappropriate mail id, kindly re-route it to
respective team.

I'm using ubuntu 18.04 and tried installing Postgresql 10, using apt-get
install postgresql
Installation went well.

When I start the service it runs fine, but when I run 
$ sudo su postgres

it takes me in, when I type psql
getting the following error,
psql: could not connect to server: No such file or directory
    Is the server running locally and accepting
    connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?

Checked for a solution all over the internet and spent almost 2 days with
this issue,
finally ran the following command 
systemctl status postgresql@10-main
below error message pops-out

● postgresql@10-main.service - PostgreSQL Cluster 10-main
   Loaded: loaded (/lib/systemd/system/postgresql@.service; indirect; vendor
preset: enabled)
   Active: failed (Result: protocol) since Thu 2019-01-10 16:21:58 IST;
17min ago
  Process: 7733 ExecStart=/usr/bin/pg_ctlcluster --skip-systemctl-redirect
10-main start (code=exited, status=1/FAILURE)

Jan 10 16:21:58 ubuntu-VirtualBox systemd[1]: Starting PostgreSQL Cluster
10-main...
Jan 10 16:21:58 ubuntu-VirtualBox postgresql@10-main[7733]: Error:
/usr/lib/postgresql/10/bin/pg_ctl /usr/lib/postgresql/10/bin/pg_ctl start -D
/var/lib/postgresql/10/main -l /var/log/postgresql/postgresql
Jan 10 16:21:58 ubuntu-VirtualBox postgresql@10-main[7733]: 2019-01-10
16:21:58.817 IST [7738] FATAL:  private key file
"/etc/ssl/private/ssl-cert-snakeoil.key" has group or world access
Jan 10 16:21:58 ubuntu-VirtualBox postgresql@10-main[7733]: 2019-01-10
16:21:58.817 IST [7738] DETAIL:  File must have permissions u=rw (0600) or
less if owned by the database user, or permissions u=rw,g=r
Jan 10 16:21:58 ubuntu-VirtualBox postgresql@10-main[7733]: 2019-01-10
16:21:58.818 IST [7738] LOG:  database system is shut down
Jan 10 16:21:58 ubuntu-VirtualBox postgresql@10-main[7733]: pg_ctl: could
not start server
Jan 10 16:21:58 ubuntu-VirtualBox postgresql@10-main[7733]: Examine the log
output.
Jan 10 16:21:58 ubuntu-VirtualBox systemd[1]: postgresql@10-main.service:
Can't open PID file /var/run/postgresql/10-main.pid (yet?) after start: No
such file or directory
Jan 10 16:21:58 ubuntu-VirtualBox systemd[1]: postgresql@10-main.service:
Failed with result 'protocol'.
Jan 10 16:21:58 ubuntu-VirtualBox systemd[1]: Failed to start PostgreSQL
Cluster 10-main.

Kindly help me out.

Thank you in advance!

Regards,
Noyal 
8754409574