On Jan 2 2019 upgraded to postgis24_10.x86_64 version 2.4.6-2.rhel7
from the pgdg10 repo.
Now, pg_dump gives me the following failure message:
pg_dump: [archiver (db)] query failed: ERROR: could not load library
undefined symbol: GEOSFrechetDistanceDensify
The following geos pacakges from pgdg10 repo were installed:
Removing the geos36 package from the system resolved the problem.
I don't believe that we've ever manually installed geos packages,
although I could be wrong. I this this situation arose in the normal
course of doing "yum upgrade".