title: package in requirements.txt, but not seen in docker
body: <p>I have valid requirements.txt file, but docker doesn't install one of packages listed in requirements</p>
  
  <p>Docker version 18.09.2
  python 3.7.3</p>
  
  <p>requirements.txt</p>
  
  <pre><code>django==2.2.2
  celery==4.2.1
  selenium==3.141.0
  BeautifulSoup4==4.7.1
  redis==3.2.0
  </code></pre>
  
  <p>Dockerfile</p>
  
  <pre><code>FROM python:3.7
  ENV PYTHONUNBUFFERED 1
  ENV DJANGO_ENV dev
  ENV DJANGO_ENV dev
  COPY ./requirements.txt /code/requirements.txt
  RUN pip3 install --upgrade pip
  RUN pip3 install -r /code/requirements.txt
  COPY . /code/
  WORKDIR /code/
  EXPOSE 8000
  
  </code></pre>
  
  <p>docker_compose.yml</p>
  
  <pre><code>version: '3'
  
  services:
    db:
      image: postgres:9.6.5
      volumes:
        - postgres_data:/var/lib/postgresql/data/
    redis:
      image: "redis:alpine"
    web:
      build: .
      command: bash -c "python /code/manage.py migrate --noinput &amp;&amp; python /code/manage.py runserver 0.0.0.0:8000"
      volumes:
        - .:/code
      ports:
        - "8000:8000"
      depends_on:
        - db
        - redis
    celery:
      build: .
      command: celery -A google_scraper worker -l info
      volumes:
        - .:/code
      depends_on:
        - db
        - redis
  
  volumes:
    postgres_data:
  </code></pre>
  
  <p>actual error while I try to run celery:</p>
  
  <p><code>ImportError: Missing redis library (pip install redis)</code></p>
  
  <p>When I run bash for docker, and install it by manual pip3 install redis - it works fine, but still it doesn't solve problem of building it, I don't have idea where I make mistake. </p>