Upgrading postgresql from version 11 to 12 results in "Your installation references loadable libraries that are missing" - postgresql

Question

I ran
brew postgresql-upgrade-database
and after a long series of updates the final results are:
==> Migrating and upgrading data...
Performing Consistency Checks
-----------------------------
Checking cluster versions ok
Checking database user is the install user ok
Checking database connection settings ok
Checking for prepared transactions ok
Checking for reg* data types in user tables ok
Checking for contrib/isn with bigint-passing mismatch ok
Checking for tables WITH OIDS ok
Checking for invalid "sql_identifier" user columns ok
Creating dump of global objects ok
Creating dump of database schemas
ok
Checking for presence of required libraries fatal
Your installation references loadable libraries that are missing from the
new installation. You can add these libraries to the new installation,
or remove the functions using them from the old installation. A list of
problem libraries is in the file:
loadable_libraries.txt
Failure, exiting
Error: Upgrading postgresql data from 11 to 12 failed!
==> Removing empty postgresql initdb database...
==> Moving postgresql data back from /usr/local/var/postgres.old to /usr/local/var/postgres...
==> Successfully started `postgresql` (label: homebrew.mxcl.postgresql)
Error: Failure while executing; `/usr/local/opt/postgresql/bin/pg_upgrade -r -b /usr/local/Cellar/postgresql#11/11.9/bin -B /usr/local/opt/postgresql/bin -d /usr/local/var/postgres.old -D /usr/local/var/postgres -j 16` exited with 1.
The only notes about this I could find were about pg developers mulling whether to print out the offending databases involved: it was unclear what the fix would be. Any hints ?
Update There is no loadable_libraries.txt in the directory that this was run.

Answer 1

I am creating an answer based on the comment from #LaurenzAlbe. The loadable_libraries.txt was not placed in the current directory from which the command
was run . Instead let's go find where it went:
$find / -name loadable_libraries.txt
/usr/local/var/log/loadable_libraries.txt
So what's in that file?
06:22:24/cidervuong2 $cat /usr/local/var/log/loadable_libraries.txt
could not load library "$libdir/pg_background": ERROR: could not access file "$libdir/pg_background": No such file or directory
Database: bluej
I looked into that error:
ERROR: could not access file "$libdir/pg_background"
and there is no useful information. I went ahead and nuked postgresql again and this time it installed cleanly.
brew uninstall --ignore-dependencies postgres
brew install postgres
brew services start postgresql # actually already started
and pg came up cleanly this time
502 84118 1 0 6:33AM ?? 0:00.03 /usr/local/opt/postgresql/bin/postgres -D /usr/local/var/postgres
502 84120 84118 0 6:33AM ?? 0:00.00 postgres: checkpointer
502 84121 84118 0 6:33AM ?? 0:00.03 postgres: background writer
502 84122 84118 0 6:33AM ?? 0:00.01 postgres: walwriter
502 84123 84118 0 6:33AM ?? 0:00.01 postgres: autovacuum launcher
502 84124 84118 0 6:33AM ?? 0:00.01 postgres: stats collector
502 84125 84118 0 6:33AM ?? 0:00.00 postgres: logical replication launcher