If you have tried to install psycopg2 (Postgresql support for python) which is used by the popular sqlalchemy framework under virtualenv you will end up with something like this

(python-keygrabber-env)goshawk@cacserver:~/python-keygrabber-env/aranciulla/keygrabber$ pip install psycopg2
Downloading/unpacking psycopg2
  Running setup.py egg_info for package psycopg2
    
    Error: pg_config executable not found.
    
    Please add the directory containing pg_config to the PATH
    or specify the full executable path with the option:
    
        python setup.py build_ext --pg-config /path/to/pg_config build ...
    
    or with the pg_config option in 'setup.cfg'.
    Complete output from command python setup.py egg_info:
    running egg_info

writing pip-egg-info/psycopg2.egg-info/PKG-INFO

writing top-level names to pip-egg-info/psycopg2.egg-info/top_level.txt

writing dependency_links to pip-egg-info/psycopg2.egg-info/dependency_links.txt

warning: manifest_maker: standard file '-c' not found



Error: pg_config executable not found.



Please add the directory containing pg_config to the PATH

or specify the full executable path with the option:



    python setup.py build_ext --pg-config /path/to/pg_config build ...



or with the pg_config option in 'setup.cfg'.

----------------------------------------
Command python setup.py egg_info failed with error code 1
Storing complete log in /home/goshawk/.pip/pip.log
(python-keygrabber-env)goshawk@cacserver:~/python-keygrabber-env/aranciulla/keygrabber$ 

Don’t worry! you need to just install two packages on your ubuntu machine: libpq-dev python-dev. To do so just type in a terminal:

sudo apt-get install libpq-dev python-dev

and thus

(python-keygrabber-env)goshawk@cacserver:~/python-keygrabber-env/aranciulla/keygrabber$ pip install psycopg2
Downloading/unpacking psycopg2
  Running setup.py egg_info for package psycopg2
    
    no previously-included directories found matching 'doc/src/_build'
    warning: no files found matching 'NEWS-2.0'
    warning: no files found matching 'NEWS-2.3'
Installing collected packages: psycopg2
  Running setup.py install for psycopg2
    building 'psycopg2._psycopg' extension
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/psycopgmodule.c -o build/temp.linux-x86_64-2.7/psycopg/psycopgmodule.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/green.c -o build/temp.linux-x86_64-2.7/psycopg/green.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/pqpath.c -o build/temp.linux-x86_64-2.7/psycopg/pqpath.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/utils.c -o build/temp.linux-x86_64-2.7/psycopg/utils.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/bytes_format.c -o build/temp.linux-x86_64-2.7/psycopg/bytes_format.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/connection_int.c -o build/temp.linux-x86_64-2.7/psycopg/connection_int.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/connection_type.c -o build/temp.linux-x86_64-2.7/psycopg/connection_type.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/cursor_int.c -o build/temp.linux-x86_64-2.7/psycopg/cursor_int.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/cursor_type.c -o build/temp.linux-x86_64-2.7/psycopg/cursor_type.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/lobject_int.c -o build/temp.linux-x86_64-2.7/psycopg/lobject_int.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/lobject_type.c -o build/temp.linux-x86_64-2.7/psycopg/lobject_type.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/notify_type.c -o build/temp.linux-x86_64-2.7/psycopg/notify_type.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/xid_type.c -o build/temp.linux-x86_64-2.7/psycopg/xid_type.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/adapter_asis.c -o build/temp.linux-x86_64-2.7/psycopg/adapter_asis.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/adapter_binary.c -o build/temp.linux-x86_64-2.7/psycopg/adapter_binary.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/adapter_datetime.c -o build/temp.linux-x86_64-2.7/psycopg/adapter_datetime.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/adapter_list.c -o build/temp.linux-x86_64-2.7/psycopg/adapter_list.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/adapter_pboolean.c -o build/temp.linux-x86_64-2.7/psycopg/adapter_pboolean.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/adapter_pdecimal.c -o build/temp.linux-x86_64-2.7/psycopg/adapter_pdecimal.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/adapter_pfloat.c -o build/temp.linux-x86_64-2.7/psycopg/adapter_pfloat.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/adapter_qstring.c -o build/temp.linux-x86_64-2.7/psycopg/adapter_qstring.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/microprotocols.c -o build/temp.linux-x86_64-2.7/psycopg/microprotocols.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/microprotocols_proto.c -o build/temp.linux-x86_64-2.7/psycopg/microprotocols_proto.o -Wdeclaration-after-statement
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4-beta2 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x080407 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/usr/include/python2.7 -I. -I/usr/include/postgresql -I/usr/include/postgresql/8.4/server -c psycopg/typecast.c -o build/temp.linux-x86_64-2.7/psycopg/typecast.o -Wdeclaration-after-statement
    gcc -pthread -shared -Wl,-O1 -Wl,-Bsymbolic-functions -Wl,-Bsymbolic-functions build/temp.linux-x86_64-2.7/psycopg/psycopgmodule.o build/temp.linux-x86_64-2.7/psycopg/green.o build/temp.linux-x86_64-2.7/psycopg/pqpath.o build/temp.linux-x86_64-2.7/psycopg/utils.o build/temp.linux-x86_64-2.7/psycopg/bytes_format.o build/temp.linux-x86_64-2.7/psycopg/connection_int.o build/temp.linux-x86_64-2.7/psycopg/connection_type.o build/temp.linux-x86_64-2.7/psycopg/cursor_int.o build/temp.linux-x86_64-2.7/psycopg/cursor_type.o build/temp.linux-x86_64-2.7/psycopg/lobject_int.o build/temp.linux-x86_64-2.7/psycopg/lobject_type.o build/temp.linux-x86_64-2.7/psycopg/notify_type.o build/temp.linux-x86_64-2.7/psycopg/xid_type.o build/temp.linux-x86_64-2.7/psycopg/adapter_asis.o build/temp.linux-x86_64-2.7/psycopg/adapter_binary.o build/temp.linux-x86_64-2.7/psycopg/adapter_datetime.o build/temp.linux-x86_64-2.7/psycopg/adapter_list.o build/temp.linux-x86_64-2.7/psycopg/adapter_pboolean.o build/temp.linux-x86_64-2.7/psycopg/adapter_pdecimal.o build/temp.linux-x86_64-2.7/psycopg/adapter_pfloat.o build/temp.linux-x86_64-2.7/psycopg/adapter_qstring.o build/temp.linux-x86_64-2.7/psycopg/microprotocols.o build/temp.linux-x86_64-2.7/psycopg/microprotocols_proto.o build/temp.linux-x86_64-2.7/psycopg/typecast.o -lpq -o build/lib.linux-x86_64-2.7/psycopg2/_psycopg.so
    
    no previously-included directories found matching 'doc/src/_build'
    warning: no files found matching 'NEWS-2.0'
    warning: no files found matching 'NEWS-2.3'
Successfully installed psycopg2
Cleaning up...
(python-keygrabber-env)goshawk@cacserver:~/python-keygrabber-env/aranciulla/keygrabber$ 

That’s all! 😀 Hope it was useful