Add support for Python 3.9.

NEWS

@@ -3,6 +3,7 @@
  * Update systemd service example to return a permission error when a system call isn't permitted
    (instead of terminating borgmatic outright).
  * Drop support for Python 3.5, which has been end-of-lifed.
+ * Add support for Python 3.9.
  * Update versions of test dependencies (test_requirements.txt and test containers).
  * Only support black code formatter on Python 3.8+. New black dependencies make installation
    difficult on older versions of Python.

test_requirements.txt

@@ -25,4 +25,4 @@ regex; python_version >= '3.8'
 requests==2.25.0
 ruamel.yaml>0.15.0,<0.17.0
 toml==0.10.2; python_version >= '3.8'
-typed-ast==1.4.1; python_version >= '3.8'
+typed-ast==1.4.2; python_version >= '3.8'

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py36,py37,py38
+envlist = py36,py37,py38,py39
 skip_missing_interpreters = True
 skipsdist = True
 minversion = 3.14.1
@@ -13,7 +13,7 @@ whitelist_externals =
 passenv = COVERAGE_FILE
 commands =
     pytest {posargs}
-    py38: black --check .
+    py38,py39: black --check .
     isort --check-only --settings-path setup.cfg .
     flake8 borgmatic tests