extract properties from certificates

[jotpe <jotpe@xxxxxxxxx>]

Hello,

I want to extract properties from x.509 certificates stored in a bytea 
column.
I found the pg-cert extension at https://github.com/beargiles/pg-cert

I have trouble to compile it. When I enter "make" following error 
message appears:

Makefile:29: /usr/lib/postgresql/9.6/lib/pgxs/src/makefiles/pgxs.mk: 
Datei oder Verzeichnis nicht gefunden
make: *** Keine Regel, um 
„/usr/lib/postgresql/9.6/lib/pgxs/src/makefiles/pgxs.mk“ zu erstellen. 
Schluss.

What am I missing?

Best regards Johannes