Use setup.cfg in Dockerfile

Dockerfile

@@ -18,7 +18,8 @@ WORKDIR /app
 
 # Cache dependencies if possible
 COPY setup.py /app
-RUN python -c 'from setup import *; print("\n".join(install_requires))' \
+COPY setup.cfg /app
+RUN python -c 'from setup import *; print_install_requires()' \
         > /tmp/requirements.txt && \
     pip install -r /tmp/requirements.txt && \
     rm /tmp/requirements.txt

setup.py

@@ -1,4 +1,10 @@
 from setuptools import setup
 
+def print_install_requires():
+    import configparser;
+    c = configparser.ConfigParser();
+    c.read('setup.cfg');
+    print(c['options']['install_requires'])
+
 if __name__ == '__main__':
     setup()