title: Failing to install psycopg2-binary on new docker container
body: <p>I have encountered a problem while trying to run my django project on a new Docker container.
  It is my first time using Docker and I can't seem to find a good way to run a django project on it. Having tried multiple tutorials, I always get the error about psycopg2 not being installed.</p>
  <p>requirements.txt:</p>
  <pre><code>-i https://pypi.org/simple
  asgiref==3.2.7
  django-cors-headers==3.3.0
  django==3.0.7
  djangorestframework==3.11.0
  gunicorn==20.0.4
  psycopg2-binary==2.8.5
  pytz==2020.1
  sqlparse==0.3.1
  </code></pre>
  <p>Dockerfile:</p>
  <pre><code># pull official base image
  FROM python:3.8.3-alpine
  
  # set work directory
  WORKDIR /usr/src/app
  
  # set environment variables
  ENV PYTHONDONTWRITEBYTECODE 1
  ENV PYTHONUNBUFFERED 1
  
  # install dependencies
  RUN pip install --upgrade pip
  
  COPY ./requirements.txt .
  RUN pip install -r requirements.txt
  
  # copy project
  COPY . .
  
  # set project environment variables
  # grab these via Python's os.environ
  # these are 100% optional here
  
  ENV PORT=8000
  ENV SECRET_KEY_TWITTER = &quot;***&quot;
  </code></pre>
  <p>While running docker-compose build, I get the following error:</p>
  <pre><code>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.
  </code></pre>
  <p>I will gladly answer any questions that might lead to the solution.
  Also, maybe someone can recommend me a good tutorial on dockerizing django apps?</p>