remove python 3.5 support

Author: Carreau

docs/release.rst

@@ -1,6 +1,11 @@
 Release notes
 =============
 
+* Remove support for Python 3.5 which is end of life. While the code base might
+  still be compatible; the source dist and wheel are marked as Python 3.6+ and
+  pip will not install them. Continuous integration on Python 3.5 has been
+  disabled.
+
 .. _release_0.7.2:
 
 0.7.2

setup.py

@@ -318,8 +318,9 @@ def run_setup(with_extensions):
         },
         ext_modules=ext_modules,
         cmdclass=cmdclass,
-        package_dir={'': '.'},
-        packages=['numcodecs', 'numcodecs.tests'],
+        package_dir={"": "."},
+        python_requires=">=3.6, <4",
+        packages=["numcodecs", "numcodecs.tests"],
         classifiers=[
             'Development Status :: 4 - Beta',
             'Intended Audience :: Developers',
@@ -330,7 +331,6 @@ def run_setup(with_extensions):
             'Topic :: Software Development :: Libraries :: Python Modules',
             'Operating System :: Unix',
             'Programming Language :: Python :: 3',
-            'Programming Language :: Python :: 3.5',
             'Programming Language :: Python :: 3.6',
             'Programming Language :: Python :: 3.7',
             'Programming Language :: Python :: 3.8',