Add support for Python 3.9. (#200)

Author: Michael Howitz

CHANGES.rst

@@ -21,9 +21,8 @@ Changes
 - Drop install dependency on ``setuptools``.
   (`#189 <https://github.com/zopefoundation/RestrictedPython/issues/189>`_)
 
-- Start supporting Python 3.9.0a5. (Be aware that this support currently only
-  makes RestrictedPython usable on Python 3.9. The security implications of
-  using Python 3.9 have not yet been checked.)
+- Add support for Python 3.9 after checking the security implications of the
+  syntax changes made in that version.
 
 
 5.0 (2019-09-03)

setup.py

@@ -53,6 +53,7 @@ def read(*rnames):
         'Programming Language :: Python :: 3.6',
         'Programming Language :: Python :: 3.7',
         'Programming Language :: Python :: 3.8',
+        'Programming Language :: Python :: 3.9',
         'Programming Language :: Python :: Implementation :: CPython',
         'Topic :: Security',
     ],