我尝试在Centos 7上的Django项目的虚拟环境中安装psycopg 2-binary（pip 3 install psycopg 2-binary），并预先安装了Postgresql 12，但出现了众所周知的错误：

Error: pg_config executable not found.

    pg_config is required to build psycopg2 from source.  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'.

    If you prefer to avoid building psycopg2 from source, please install the PyPI
    'psycopg2-binary' package instead.

我尝试安装python3-devel postgresql-libs postgresql-server postgresql-devel postgresql-contrib，但仍然有这个错误。
pip 3安装psycopg 2，pip安装psycopg 2-同样的问题。
PS通过更新pip（pip安装--升级pip）解决了问题。