Fixing error when installing PostgreSQL gem in Ubuntu 15.10

InstallingPostgreqSQLGem.sh

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# Copyright (c) 2016 Ricardo Giaviti
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# We try to install the PostgreSQL gem in Ubuntu 15.10 (PostgreSQL are running in a docker conatiner), 
# but something bad happens
$ gem install pg

Building native extensions.  This could take a while...
ERROR:  Error installing pg:
	ERROR: Failed to build gem native extension.
 
    current directory: /home/rgiaviti/.rvm/gems/ruby-2.3.0/gems/pg-0.18.4/ext
/home/rgiaviti/.rvm/rubies/ruby-2.3.0/bin/ruby -r ./siteconf20160419-11751-1mpjarv.rb extconf.rb
checking for pg_config... no
No pg_config... trying anyway. If building fails, please try again with
 --with-pg-config=/path/to/pg_config
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/rgiaviti/.rvm/rubies/ruby-2.3.0/bin/$(RUBY_BASE_NAME)
	--with-pg
	--without-pg
	--enable-windows-cross
	--disable-windows-cross
	--with-pg-config
	--without-pg-config
	--with-pg_config
	--without-pg_config
	--with-pg-dir
	--without-pg-dir
	--with-pg-include
	--without-pg-include=${pg-dir}/include
	--with-pg-lib
	--without-pg-lib=${pg-dir}/lib
 
To see why this extension failed to compile, please check the mkmf.log which can be found here:
 
  /home/rgiaviti/.rvm/gems/ruby-2.3.0/extensions/x86_64-linux/2.3.0/pg-0.18.4/mkmf.log
 
extconf failed, exit code 1
 
Gem files will remain installed in /home/rgiaviti/.rvm/gems/ruby-2.3.0/gems/pg-0.18.4 for inspection.
Results logged to /home/rgiaviti/.rvm/gems/ruby-2.3.0/extensions/x86_64-linux/2.3.0/pg-0.18.4/gem_make.out

# So, we need a specific package to install this gem and build the native extensions
$ sudo apt-get install libpq-dev

# And, we try again:
$ gem install pg

# Finally, we are good to create a new rails app with postgresql
$ rails new myapp --database=postgresql