pg_upgrade and missing loadable libraries

I have seen a few reports where people are getting this pg_upgrade
error:

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

and the file contains:

could not load library "$libdir/pgpool-regclass":
ERROR: could not access file "$libdir/pgpool-regclass": No such file or directory

The problem is that there is no indicate of which database to look in.
Should we adjust the output to suggest the first database that has it,
or update the instructions to mention they have to look in all
databases, and give them some instructions on finding the problem?

This seems to be one of the last pg_upgrade problems, along with
preserving optimizer statistics, which I am hoping to do for PG 11.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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