title: Install pip package when already satisfied by distro package
body: <p>I have something like the following in my Dockerfile:</p>
  <pre><code>ADD api/requirements.txt /app/
  
  # Install apt and pip packages
  RUN set -ex \
      &amp;&amp; BUILD_DEPS=&quot; \
          build-essential \
          gcc \
          python3-dev \
          libsasl2-dev libldap2-dev libssl-dev \
          libpq-dev libffi-dev \
          python3 python3-pip python3-wheel python3-setuptools \
          zlib1g-dev libjpeg-dev libpng-dev \
      &quot; \
      &amp;&amp; RUN_DEPS=&quot; \
          postgresql-client \
          nginx \
          libsasl2-dev libldap2-dev libssl-dev python3-dev \
          python3 python3-pip python3-setuptools python3-wheel \
          wireguard \
          gunicorn3 \
          curl \
          zlib1g-dev libjpeg-dev libpng-dev \
      &quot; \
      &amp;&amp; apt-get update &amp;&amp; apt-get install -y $BUILD_DEPS \
      &amp;&amp; pip3 install --no-cache-dir --default-timeout=100000 -r /app/requirements.txt \
      &amp;&amp; apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false  $BUILD_DEPS \
      &amp;&amp; apt-get update &amp;&amp; apt-get install -y --no-install-recommends $RUN_DEPS \
      &amp;&amp; rm -rf /var/lib/apt/lists/*
  </code></pre>
  <p>One pypackage I have in my <code>requirements.txt</code> is <code>six</code>.  However, the debian package <code>python3-six</code> is a dependency of one of those packages in <code>BUILD_DEPS</code>.  This means that when it runs <code>pip install -r requirements.txt</code>, it skips installing <code>six</code> as it's already supplied by the distro package.</p>
  <p>Is there a way to force that pypackage to install anyway?</p>