hi i use
CentOS release 6.8 (Final)
i use THIS guide from digitalocean to install discourse
in installation i install pgsql-9.6  and now when i want to run
    bundle install --deployment
show me this error
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.
/home/discourse/.rvm/rubies/ruby-2.0.0-p648/bin/ruby -r ./siteconf20161119-10988-nqqoxr.rb extconf.rb --with-pgsql-lib=/usr/pgsql-9.1/lib
--with-pg-config=/usr/pgsql-9.1/bin/pg_config
Using config values from /usr/pgsql-9.1/bin/pg_config
sh: /usr/pgsql-9.1/bin/pg_config: No such file or directory
sh: /usr/pgsql-9.1/bin/pg_config: No such file or directory
checking for libpq-fe.h... no
Can't find the 'libpq-fe.h header
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers.  Check the mkmf.log file for more details.  You may
need configuration options.
Provided configuration options:
	--with-opt-dir
	--without-opt-dir
	--with-opt-include
	--without-opt-include=${opt-dir}/include
	--with-opt-lib
	--without-opt-lib=${opt-dir}/lib
	--with-make-prog
	--without-make-prog
	--srcdir=.
	--curdir
	--ruby=/home/discourse/.rvm/rubies/ruby-2.0.0-p648/bin/ruby
	--with-pg
	--without-pg
	--enable-windows-cross
	--disable-windows-cross
	--with-pg-config
	--with-pg-dir
	--without-pg-dir
	--with-pg-include
	--without-pg-include=${pg-dir}/include
	--with-pg-lib
	--without-pg-lib=${pg-dir}/
extconf failed, exit code 1
Gem files will remain installed in /var/discourse/vendor/bundle/ruby/2.0.0/gems/pg-0.19.0 for inspection.
Results logged to /var/discourse/vendor/bundle/ruby/2.0.0/extensions/x86_64-linux/2.0.0/pg-0.19.0/gem_make.out
An error occurred while installing pg (0.19.0), and Bundler cannot continue.
Make sure that `gem install pg -v '0.19.0'` succeeds before bundling.
            