/usr/share/postgresql/9.4/extension/pgespresso.control is in postgresql-9.4-pgespresso 1.0-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | comment = 'pgespresso extension for Barman backups'
default_version = '1.0'
module_pathname = '$libdir/pgespresso'
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