Postgres 9.6.6 on Ubuntu 16.04, lots of errors
Having talked about this on freenode (thanks Andrew!) I modified two of the default settings in postgresql.conf, and that made the issues go away without causing other ill effects.

autovacuum_vacuum_cost_delay = 0ms
deadlock_timeout = 5s


I think the consensus is still that pscheduler's attempts to get table locks so frequently is poor design, but the workaround above seems to be doing the trick for the time being.