fixup! setup.py: Move all configuration to setup.cfg

setup.cfg

@@ -33,5 +33,3 @@ setup_requires =
     pytest-runner
 
 python_requires = >= 3.6
-install_requires = file: requirements.txt
-tests_require = file: requirements-tests.txt

setup.py

@@ -1,5 +1,20 @@
 #!/usr/bin/env python3
 from setuptools import setup
 
+
+def requirements(section=None):
+    """Helper for loading dependencies from requirements files."""
+    if section is None:
+        filename = "requirements.txt"
+    else:
+        filename = f"requirements-{section}.txt"
+
+    with open(filename) as file:
+        return [line.strip() for line in file]
+
+
 # See setup.cfg for the actual configuration.
-setup()
+setup(
+    install_requires=requirements(),
+    tests_require=requirements('tests'),
+)