Introduce py39 for unittests

This update is to introduce py39 for unittest via tox. After installing
python3.9, you can run tests with py39.

  # Run unittests with py39
  $ tox -e py39
  # or debug
  $ tox -e debug-py39

For the update, replace `base64.encodestring` with `base64.encodebytes`
because it has been a deplicated alias and removed in python3.9.

Change-Id: I1ea2e4fb836c485cfe7690c3bf8a0791ced655d5
Signed-off-by: Yasufumi Ogawa <yasufum.o@gmail.com>

tacker/glance_store/store.py

@@ -150,6 +150,6 @@ def _add_basic_auth(request, username, password):
 
     This function adds basic authentication information to a urllib request.
     """
-    auth_str = base64.encodestring(('%s:%s' % (
+    auth_str = base64.encodebytes(('%s:%s' % (
         username, password)).encode()).decode().strip()
     request.add_header('Authorization', 'Basic %s' % auth_str)

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py38,py36,pep8,docs
+envlist = py39,py38,py36,pep8,docs
 minversion = 3.1.1
 skipsdist = True
 ignore_basepython_conflict = True
@@ -40,6 +40,10 @@ commands = oslo_debug_helper {posargs}
 basepython = python3.6
 commands = oslo_debug_helper {posargs}
 
+[testenv:debug-py39]
+basepython = python3.9
+commands = oslo_debug_helper {posargs}
+
 [testenv:pep8]
 deps = -r{toxinidir}/doc/requirements.txt
        -r{toxinidir}/test-requirements.txt