title: docker can't build because of alpine error
body: <p>Hi I am trying build a docker and Docker file looks like this.</p>
  
  <pre><code>FROM alpine
  
  LABEL description "Nginx + uWSGI + Flask based on Alpine Linux and managed by Supervisord"
  
  # Copy python requirements file
  COPY requirements.txt /tmp/requirements.txt
  
  RUN apk add --no-cache \
      python3 \
      bash \
      nginx \
      uwsgi \
      uwsgi-python3 \
      supervisor &amp;&amp; \
      python3 -m ensurepip &amp;&amp; \
      rm -r /usr/lib/python*/ensurepip &amp;&amp; \
      pip3 install --upgrade pip setuptools &amp;&amp; \
      pip3 install -r /tmp/requirements.txt &amp;&amp; \
      rm /etc/nginx/conf.d/default.conf &amp;&amp; \
      rm -r /root/.cache
  
  # Copy the Nginx global conf
  COPY nginx.conf /etc/nginx/
  # Copy the Flask Nginx site conf
  COPY flask-site-nginx.conf /etc/nginx/conf.d/
  # Copy the base uWSGI ini file to enable default dynamic uwsgi process number
  COPY uwsgi.ini /etc/uwsgi/
  # Custom Supervisord config
  COPY supervisord.conf /etc/supervisord.conf
  
  # Add demo app
  COPY ./app /app
  WORKDIR /app
  
  CMD ["/usr/bin/supervisord"]
  </code></pre>
  
  <p>Errors looks like</p>
  
  <pre><code>Sending build context to Docker daemon  250.9kB
  Step 1/11 : FROM alpine
   ---&gt; 196d12cf6ab1
  Step 2/11 : LABEL description "Nginx + uWSGI + Flask based on Alpine Linux and managed by Supervisord"
   ---&gt; Using cache
   ---&gt; d8d38c761b8d
  Step 3/11 : COPY requirements.txt /tmp/requirements.txt
   ---&gt; Using cache
   ---&gt; cb29eb34ca46
  Step 4/11 : RUN apk add --no-cache     python3     bash     nginx     uwsgi     uwsgi-python3     supervisor &amp;&amp;     python3 -m ensurepip &amp;&amp;     rm -r /usr/lib/python*/ensurepip &amp;&amp;     pip3 install --upgrade pip setuptools &amp;&amp;     pip3 install -r /tmp/requirements.txt &amp;&amp;     rm /etc/nginx/conf.d/default.conf &amp;&amp;     rm -r /root/.cache
   ---&gt; Running in 3d568d2620dd
  fetch http://dl-cdn.alpinelinux.org/alpine/v3.8/main/x86_64/APKINDEX.tar.gz
  WARNING: Ignoring http://dl-cdn.alpinelinux.org/alpine/v3.8/main/x86_64/APKINDEX.tar.gz: could not connect to server (check repositories file)
  fetch http://dl-cdn.alpinelinux.org/alpine/v3.8/community/x86_64/APKINDEX.tar.gz
  WARNING: Ignoring http://dl-cdn.alpinelinux.org/alpine/v3.8/community/x86_64/APKINDEX.tar.gz: could not connect to server (check repositories file)
  ERROR: unsatisfiable constraints:
    bash (missing):
      required by: world[bash]
    nginx (missing):
      required by: world[nginx]
    python3 (missing):
      required by: world[python3]
    supervisor (missing):
      required by: world[supervisor]
    uwsgi (missing):
      required by: world[uwsgi]
    uwsgi-python3 (missing):
      required by: world[uwsgi-python3]
  The command '/bin/sh -c apk add --no-cache     python3     bash     nginx     uwsgi     uwsgi-python3     supervisor &amp;&amp;     python3 -m ensurepip &amp;&amp;     rm -r /usr/lib/python*/ensurepip &amp;&amp;     pip3 install --upgrade pip setuptools &amp;&amp;     pip3 install -r /tmp/requirements.txt &amp;&amp;     rm /etc/nginx/conf.d/default.conf &amp;&amp;     rm -r /root/.cache' returned a non-zero code: 6
  </code></pre>
  
  <p>A month ago it was building fine. Because of the limited knowledge in Docker i couldn't to figure what's causing the error.  A quick google search has resulted in these two links: <a href="https://github.com/gliderlabs/docker-alpine/issues/279" rel="noreferrer">link1</a> <a href="https://github.com/gliderlabs/docker-alpine/issues/191" rel="noreferrer">link2</a> But none of them were working.</p>