在ubuntu 18.04上使用pip3安装psycopg2的时候通常会报如下错误：
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: b'You need to install postgresql-server-dev-NN for building a server-side extension or libpq-dev for building a client-side application.\n'
看最后一行的错误提示，是需要其它扩展程序，根据它的提示，选择了安装libpq-dev，如下：
apt install libpq-dev
安装成功后再执行pip3 install psyconpg2即可成功安装
