Add fake setup.py to make GitHub recognize us

pyproject.toml

@@ -70,7 +70,12 @@ include = [
     "docs",
     "tests",
 ]
-exclude = ["docs/_build", "tests/__pycache__", "tests/.mypy_cache"]
+exclude = [
+    "setup.py",          # Just a fake stub to make GitHub recognize us.
+    "docs/_build",
+    "tests/__pycache__",
+    "tests/.mypy_cache",
+]
 
 
 [tool.pytest.ini_options]

setup.py

@@ -0,0 +1,32 @@
+import sys
+
+from setuptools import setup
+
+
+sys.stderr.write(
+    """
+===============================
+Unsupported installation method
+===============================
+
+argon2-cffi no longer supports installation with `python setup.py install`.
+Please use `python -m pip install .` instead.
+"""
+)
+sys.exit(1)
+
+
+# The below code will never execute, however GitHub is particularly
+# picky about where it finds Python packaging metadata.
+# See: https://github.com/github/feedback/discussions/6456
+#
+# To be removed once GitHub catches up.
+
+setup(
+    name="argon2-cffi",
+    install_requires=[
+        "argon2-cffi-bindings",
+        "dataclasses; python_version < '3.7'",
+        "typing-extensions; python_version < '3.8'",
+    ],
+)