/usr/share/postgresql/9.4/psqlrc.sample is in postgresql-client-9.4 9.4.18-0+deb8u1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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-- system-wide psql configuration file
--
-- This file is read before the .psqlrc file in the user's home directory.
--
-- Copy this to your installation's sysconf directory and rename it psqlrc.
-- The sysconf directory can be identified via "pg_config --sysconfdir".
--
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