安装psycopy2遇到的问题: pg_config executable not found
解决：pg_config is in postgresql-devel
关于postgresql-devel
The postgresql-devel package contains the header files and libraries
needed to compile C or C++ applications which will directly interact
with a PostgreSQL database management server. It also contains the ecpg
Embedded C Postgres preprocessor. You need to install this package if you want
to develop applications which will interact with a PostgreSQL server.
在Debian/Ubuntu上：
安装libpq-dev
sudo apt-get install libpq-dev
在Centos/Fedora/Cygwin/Babun上：
安装libpq-devel
sudo yum install libpq-devel
