title: App Engine Flexible - Docker file fails to install GDAL
body: <p>I am trying to deploy a Django application to App Engine Flexible Environment. My dockerfile is failing to install GDAL. </p>
  
  <p>This is the error message that i get when running <code>gcloud app deploy</code>:</p>
  
  <pre><code>  File "/env/lib/python3.7/site-packages/django/contrib/gis/gdal/libgdal.py", line 42, in &lt;module&gt;
      % '", "'.join(lib_names)
  django.core.exceptions.ImproperlyConfigured: Could not find the GDAL library (tried "gdal", "GDAL", "gdal2.4.0", "gdal2.3.0", "gdal2.2.0", "gdal2.1.0", "gdal2.0.0"). Is GDAL installed? If it is, try setting GDAL_LIBRARY_PATH in your settings.
  [2020-04-24 16:12:26 +0000] [8] [INFO] Worker exiting (pid: 8)
  [2020-04-24 16:12:26 +0000] [1] [INFO] Shutting down: Master
  [2020-04-24 16:12:26 +0000] [1] [INFO] Reason: Worker failed to boot.
  </code></pre>
  
  <p>This is my dockerfile: </p>
  
  <pre><code>FROM ubuntu:bionic
  
  RUN apt-get update &amp;&amp; apt-get install -y \
    binutils \
    gdal-bin \
    python3-gdal \
    ibgdal-dev \
    libproj-dev
  
  # Create a virtualenv for dependencies. This isolates these packages from
  # system-level packages.
  # Use -p python3 or -p python3.7 to select python version. Default is version 2.
  RUN virtualenv /env -p python3.7
  
  
  
  # Setting these environment variables are the same as running
  # source /env/bin/activate.
  ENV VIRTUAL_ENV /env
  ENV PATH /env/bin:$PATH
  
  # Copy the application's requirements.txt and run pip to install all
  # dependencies into the virtualenv.
  RUN pip install -r requirements.txt
  
  # Add the application source code.
  ADD . /
  
  
  # Run a WSGI server to serve the application. gunicorn must be declared as
  # a dependency in requirements.txt.
  CMD gunicorn -b :$PORT main:app
  </code></pre>
  
  <p>and this is my app.yaml:</p>
  
  <pre><code>runtime: python
  env: flex
  entrypoint: gunicorn -b :$PORT main:app
  
  runtime_config:
    # You can also specify 2 for Python 2.7
    python_version: 3.7
  </code></pre>
  
  <p>I am aware that I am asking a very similar question that being answered <a href="https://stackoverflow.com/questions/61390259/app-engine-flexible-environment-dockerfile-installing-outdated-version-of-gdal">here</a>, but the askers own solution doesn't seem to be working. </p>