pip install failed

[ashbyp]

After running pip install -r requirements.txt
Using cached https://files.pythonhosted.org/packages/86/fd/cc8315be63a41fe000cce20482a917e874cdc1151e62cb0141f5e55f711e/psycopg2-2.6.1.tar.gz
Complete output from command python setup.py egg_info:
running egg_info
creating pip-egg-info\psycopg2.egg-info
writing pip-egg-info\psycopg2.egg-info\PKG-INFO
writing dependency_links to pip-egg-info\psycopg2.egg-info\dependency_links.txt
writing top-level names to pip-egg-info\psycopg2.egg-info\top_level.txt
writing manifest file 'pip-egg-info\psycopg2.egg-info\SOURCES.txt'
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'.

----------------------------------------

[branky]

need to upgrade psycopg2 to higher version
I changed to psycopg2==2.7.3.1 in requirements.txt and the pip install succeed.