title: Package missing in Alpine Linux even though it's listed on package repo website
body: <p>I am attempting to build out a Docker container that runs Alpine Linux with GDAL and the necessary Python hooks:</p>
  
  <pre><code>FROM python:3.6-alpine
  
  RUN apk update
  
  RUN apk add py-gdal gdal
  
  RUN pip install uwsgi
  
  RUN mkdir /code
  WORKDIR /code
  COPY requirements.txt .
  
  RUN pip install -r requirements.txt
  
  COPY . .
  
  CMD ["uwsgi", "--ini", "uwsgi.ini"]
  </code></pre>
  
  <p>As you can see, I'm running both an <code>apk update</code> statement to update repos, and then <code>apk add</code> statements to install the packages. Here is the output I receive:</p>
  
  <pre><code>/usr/bin/make -f /Users/some_guy/Workspace/tagging_tracker_backend/Makefile build up
  Pulling nginx ... 
  Pulling db    ... 
  Pulling web   ... 
  db uses an image, skipping
  Building nginx
  Step 1/3 : FROM nginx:1.15
   ---&gt; 7042885a156a
  Step 2/3 : RUN rm /etc/nginx/conf.d/default.conf
   ---&gt; Using cache
   ---&gt; 97782a5dae3a
  Step 3/3 : COPY nginx.conf /etc/nginx/conf.d/tag.conf
   ---&gt; Using cache
   ---&gt; 3158ab7993cd
  Successfully built 3158ab7993cd
  Building web
  Successfully tagged tagging_tracker_backend_nginx:latest
  Step 1/10 : FROM python:3.6-alpine
   ---&gt; de35df1f34dd
  Step 2/10 : RUN apk update
   ---&gt; Using cache
   ---&gt; 15477d802b32
  Step 3/10 : RUN apk add py-gdal gdal
   ---&gt; Running in 77bef31e5d15
  ERROR: unsatisfiable constraints:
    gdal (missing):
      required by: world[gdal]
    py-gdal (missing):
      required by: world[py-gdal]
  Service 'web' failed to build: The command '/bin/sh -c apk add py-gdal gdal' returned a non-zero code: 2
  make: *** [build] Error 1
  
  Process finished with exit code 2
  </code></pre>
  
  <p>Both of these packages can be found at <a href="https://pkgs.alpinelinux.org/package/edge/testing/x86_64/gdal" rel="noreferrer">the Alpine Linux package website</a>.</p>
  
  <p>I'm not familiar with Alpine Linux but am used to installing packages on other types of Linux. Is there another command that needs to be passed in here?</p>