title: Docker/Rocker - unable to locate package python3.8
body: <p>I am trying to install python3.8 in my container. My base image is rocker/shiny. I was able to build my image and start my container two weeks ago successfully, but am unable to do so today and am getting the following error message:</p>
  <p><code>E: Unable to locate package python3.8</code>
  <code>E: Couldn't find any package by regex 'python3.8'</code></p>
  <p>Furthermore, other folks who try to build this Dockerfile on their computers are getting the same error message.</p>
  <p>Here is my Dockerfile</p>
  <pre><code># base image
  FROM rocker/shiny:3.3.2
  
  RUN apt-get update &amp;&amp; apt-get install -y \
      sudo \
      python3.8 \
      python3-dev \
      libpq-dev \
      python3-pip \
      libxml2-dev
  
  COPY . /srv/shiny-server/app
  
  WORKDIR /srv/shiny-server/app
  
  RUN pip3 install --no-cache-dir -r requirements.txt
  
  EXPOSE 3838
  
  CMD [&quot;R&quot;, &quot;-e&quot;, &quot;shiny::runApp('/srv/shiny-server/app',port = 3838, host = '0.0.0.0')&quot;]
  </code></pre>
  <p>What I've tried:</p>
  <p>-Changing <code>python3.8</code> to <code>python3.8-venv</code></p>
  <p>-Changed <code>rocker/shiny:latest</code> to <code>rocker/shiny:3.3.2</code></p>