Comment 2 for bug 1838246

I just disbaled ipv6 on a plain bionic system, with the released package of nginx (no updates), and nginx fails to start with the same error, so this is not a regression introduced in a bionic update:

root@bionic-nginx:~# service nginx status
● nginx.service - A high performance web server and a reverse proxy server
   Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Tue 2019-07-30 13:19:01 UTC; 16s ago
     Docs: man:nginx(8)
  Process: 700 ExecStartPre=/usr/sbin/nginx -t -q -g daemon on; master_process on; (code=exited, status=1/FAILURE)

Jul 30 13:19:01 bionic-nginx systemd[1]: Starting A high performance web server and a reverse proxy server...
Jul 30 13:19:01 bionic-nginx nginx[700]: nginx: [emerg] socket() [::]:80 failed (97: Address family not supported by protocol)
Jul 30 13:19:01 bionic-nginx nginx[700]: nginx: configuration file /etc/nginx/nginx.conf test failed
Jul 30 13:19:01 bionic-nginx systemd[1]: nginx.service: Control process exited, code=exited status=1
Jul 30 13:19:01 bionic-nginx systemd[1]: nginx.service: Failed with result 'exit-code'.
Jul 30 13:19:01 bionic-nginx systemd[1]: Failed to start A high performance web server and a reverse proxy server.

root@bionic-nginx:~# apt-cache policy nginx
nginx:
  Installed: 1.14.0-0ubuntu1
  Candidate: 1.14.0-0ubuntu1
  Version table:
 *** 1.14.0-0ubuntu1 500
        500 http://br.archive.ubuntu.com/ubuntu bionic/main amd64 Packages
        100 /var/lib/dpkg/status

root@bionic-nginx:~# ifconfig
ens3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
        inet 192.168.122.176 netmask 255.255.255.0 broadcast 192.168.122.255
        ether 52:54:00:0d:cf:78 txqueuelen 1000 (Ethernet)
        RX packets 301 bytes 27646 (27.6 KB)
        RX errors 0 dropped 40 overruns 0 frame 0
        TX packets 181 bytes 29753 (29.7 KB)
        TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
        inet 127.0.0.1 netmask 255.0.0.0
        loop txqueuelen 1000 (Local Loopback)
        RX packets 92 bytes 6972 (6.9 KB)
        RX errors 0 dropped 0 overruns 0 frame 0
        TX packets 92 bytes 6972 (6.9 KB)
        TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

root@bionic-nginx:~# cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-4.15.0-55-generic root=UUID=ab05b2c3-a580-4df1-9ef9-0f0c5a183949 ro ipv6.disable=1 console=tty1 console=ttyS0