postgresql-11 installation errors via deb package on ubuntu 16

Hey Guys,

I hope this is the right dist.

i am installing postgresql-11 via
deb http://apt.postgresql.org/pub/repos/apt/ xenial-pgdg main 11

on a ubuntu16 xenial machine.
Let me know if this is not the right list, and i'll try to search the
right list.

we are having issues reported similar to
https://stackoverflow.com/questions/2748607/how-to-thoroughly-purge-and-reinstall-postgresql-on-ubuntu
which was ages back :) , but it is repeated.

the error messages:
error messages from /var/log/apt/term.log

Preparing to unpack .../postgresql-11_11.2-1.pgdg16.04+1_amd64.deb ...
Unpacking postgresql-11 (11.2-1.pgdg16.04+1) ...
Processing triggers for postgresql-common (199.pgdg16.04+1) ...
Building PostgreSQL dictionaries from installed myspell/hunspell packages...
Removing obsolete dictionary files:
Setting up postgresql-11 (11.2-1.pgdg16.04+1) ...
Unescaped left brace in regex is deprecated, passed through in regex;
marked by <-- HERE in m/(?<!\\)\${ <-- HERE ([^}]+)}/ at
/usr/sbin/pam_getenv line 78.
Unescaped left brace in regex is deprecated, passed through in regex;
marked by <-- HERE in m/(?<!\\)\${ <-- HERE ([^}]+)}/ at
/usr/sbin/pam_getenv line 78.
Unescaped left brace in regex is deprecated, passed through in regex;
marked by <-- HERE in m/(?<!\\)\${ <-- HERE ([^}]+)}/ at
/usr/sbin/pam_getenv line 78.
Unescaped left brace in regex is deprecated, passed through in regex;
marked by <-- HERE in m/(?<!\\)\${ <-- HERE ([^}]+)}/ at
/usr/sbin/pam_getenv line 78.
Unescaped left brace in regex is deprecated, passed through in regex;
marked by <-- HERE in m/(?<!\\)\${ <-- HERE ([^}]+)}/ at
/usr/sbin/pam_getenv line 78.
Unescaped left brace in regex is deprecated, passed through in regex;
marked by <-- HERE in m/(?<!\\)\${ <-- HERE ([^}]+)}/ at
/usr/sbin/pam_getenv line 78.
Unescaped left brace in regex is deprecated, passed through in regex;
marked by <-- HERE in m/(?<!\\)\${ <-- HERE ([^}]+)}/ at
/usr/sbin/pam_getenv line 78.
Unescaped left brace in regex is deprecated, passed through in regex;
marked by <-- HERE in m/(?<!\\)\${ <-- HERE ([^}]+)}/ at
/usr/sbin/pam_getenv line 78.
Unescaped left brace in regex is deprecated, passed through in regex;
marked by <-- HERE in m/(?<!\\)\${ <-- HERE ([^}]+)}/ at
/usr/sbin/pam_getenv line 78.
Unescaped left brace in regex is deprecated, passed through in regex;
marked by <-- HERE in m/(?<!\\)\${ <-- HERE ([^}]+)}/ at
/usr/sbin/pam_getenv line 78.
Unescaped left brace in regex is deprecated, passed through in regex;
marked by <-- HERE in m/(?<!\\)\${ <-- HERE ([^}]+)}/ at
/usr/sbin/pam_getenv line 78.
Unescaped left brace in regex is deprecated, passed through in regex;
marked by <-- HERE in m/(?<!\\)\${ <-- HERE ([^}]+)}/ at
/usr/sbin/pam_getenv line 78.
Unescaped left brace in regex is deprecated, passed through in regex;
marked by <-- HERE in m/(?<!\\)\${ <-- HERE ([^}]+)}/ at
/usr/sbin/pam_getenv line 78.
Unescaped left brace in regex is deprecated, passed through in regex;
marked by <-- HERE in m/(?<!\\)\${ <-- HERE ([^}]+)}/ at
/usr/sbin/pam_getenv line 78.
Unescaped left brace in regex is deprecated, passed through in regex;
marked by <-- HERE in m/(?<!\\)\${ <-- HERE ([^}]+)}/ at
/usr/sbin/pam_getenv line 78.
Configuring already existing cluster (configuration:
/etc/postgresql/11/main, data: /var/lib/postgresql/11/main, owner:
112:118)
Error: move_conffile: required configuration file
/var/lib/postgresql/11/main/postgresql.conf does not exist
Error: could not create default cluster. Please create it manually with

pg_createcluster 11 main --start

----
all installation happen via
deb http://apt.postgresql.org/pub/repos/apt/ xenial-pgdg main 11

while monitoring /var/lib/postgresql folder (during the
postgresql-common and postgresql-11 installation)
i do not see creation of /var/lib/postgresql/11/main/postgresql.conf at all.
and since the config is not created
pg_createcluster fails as it could not move this config to
/etc/postgresql/11/main/postgresql.conf

and hence the above error.
i guess for some reason, initdb? is not able to generate the default configs?
i am not able to reproduce this, it happends only occasionally, (1 in
5 runs) but breaks out automation of server provisioning :(

in a good run, this is what we see

fixing permissions on existing directory /var/lib/postgresql/11/main ... ok
creating subdirectories ... ok
selecting default max_connections ... 100
selecting default shared_buffers ... 128MB
selecting dynamic shared memory implementation ... posix
creating configuration files ... ok
running bootstrap script ... ok
performing post-bootstrap initialization ... ok
syncing data to disk ... ok

Success. You can now start the database server using:

/usr/lib/postgresql/11/bin/pg_ctl -D /var/lib/postgresql/11/main
-l logfile start

Ver Cluster Port Status Owner Data directory Log file
ESC[31m11 main 5432 down postgres /var/lib/postgresql/11/main
/var/log/postgresql/postgresql-11-main.logESC[0m
update-alternatives: using
/usr/share/postgresql/11/man/man1/postmaster.1.gz to provide
/usr/share/man/man1/postmaster.1.gz (postmaster.1.gz) in auto mode

https://doxygen.postgresql.org/initdb_8c.html#aa3dcebf3471677bce0aaceeaec0e8fa6
is this the code block that is create the datadir and default configs?

I'll be happy to be told i am doing things incorrectly if that is the case.

Regards,
Vijay