【pg_config executable not found.】DjangoアプリをHerokuにデプロイする時のエラー。

前提・実現したいこと

上記２つの記事を参考にDjangoで作ったアプリをherokuにデプロイしようとしています。

発生している問題・エラーメッセージ

ターミナルにて
pip install gunicorn django-heroku
を実行したところ、下記のようなエラーが出ます。

Error: pg_config executable not found.
から、pg_configにPATHが通ってないのかなと思ったりしましたが、初学者のため、調べてもよく分からず、ご質問させていただいています。

If you prefer to avoid building psycopg2 from source, please install the PyPI
'psycopg2-binary' package instead.
このメッセージから、
sudo pip install psycopg2-binary
を実行して、再度
pip install gunicorn django-heroku
としても同じエラーが出ます。

Requirement already satisfied: gunicorn in ./env/lib/python3.6/site-packages (20.0.4)
Collecting django-heroku
  Using cached django_heroku-0.3.1-py2.py3-none-any.whl (6.2 kB)
Requirement already satisfied: setuptools>=3.0 in ./env/lib/python3.6/site-packages (from gunicorn) (45.2.0)
Collecting psycopg2
  Using cached psycopg2-2.8.4.tar.gz (377 kB)
    ERROR: Command errored out with exit status 1:
     command: /Users/yudai/Desktop/instant-django-master/env/bin/python3 -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/private/var/folders/py/g02_syxj61n8bjwfdd0f2m740000gn/T/pip-install-3d4_qmnp/psycopg2/setup.py'"'"'; __file__='"'"'/private/var/folders/py/g02_syxj61n8bjwfdd0f2m740000gn/T/pip-install-3d4_qmnp/psycopg2/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base /private/var/folders/py/g02_syxj61n8bjwfdd0f2m740000gn/T/pip-install-3d4_qmnp/psycopg2/pip-egg-info
         cwd: /private/var/folders/py/g02_syxj61n8bjwfdd0f2m740000gn/T/pip-install-3d4_qmnp/psycopg2/
    Complete output (23 lines):
    running egg_info
    creating /private/var/folders/py/g02_syxj61n8bjwfdd0f2m740000gn/T/pip-install-3d4_qmnp/psycopg2/pip-egg-info/psycopg2.egg-info
    writing /private/var/folders/py/g02_syxj61n8bjwfdd0f2m740000gn/T/pip-install-3d4_qmnp/psycopg2/pip-egg-info/psycopg2.egg-info/PKG-INFO
    writing dependency_links to /private/var/folders/py/g02_syxj61n8bjwfdd0f2m740000gn/T/pip-install-3d4_qmnp/psycopg2/pip-egg-info/psycopg2.egg-info/dependency_links.txt
    writing top-level names to /private/var/folders/py/g02_syxj61n8bjwfdd0f2m740000gn/T/pip-install-3d4_qmnp/psycopg2/pip-egg-info/psycopg2.egg-info/top_level.txt
    writing manifest file '/private/var/folders/py/g02_syxj61n8bjwfdd0f2m740000gn/T/pip-install-3d4_qmnp/psycopg2/pip-egg-info/psycopg2.egg-info/SOURCES.txt'
    
    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.
    
    For further information please check the 'doc/src/install.rst' file (also at
    <http://initd.org/psycopg/docs/install.html>).
    
    ----------------------------------------
ERROR: Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.