vagrant: use py369 for binary build, add py380 for tests

Vagrantfile

@@ -138,8 +138,9 @@ end
 def install_pythons(boxname)
   return <<-EOF
     . ~/.bash_profile
+    pyenv install 3.8.0  # tests, version supporting openssl 1.1
     pyenv install 3.7.0  # tests, version supporting openssl 1.1
-    pyenv install 3.6.8  # binary build, tests, version supporting openssl 1.1
+    pyenv install 3.6.9  # binary build, tests, version supporting openssl 1.1
     pyenv install 3.5.3  # tests, 3.5.3 is first to support openssl 1.1
     pyenv rehash
   EOF
@@ -158,8 +159,8 @@ def build_pyenv_venv(boxname)
     . ~/.bash_profile
     cd /vagrant/borg
     # use the latest 3.6 release
-    pyenv global 3.6.8
-    pyenv virtualenv 3.6.8 borg-env
+    pyenv global 3.6.9
+    pyenv virtualenv 3.6.9 borg-env
     ln -s ~/.pyenv/versions/borg-env .
   EOF
 end
@@ -219,8 +220,8 @@ def run_tests(boxname)
     . ../borg-env/bin/activate
     if which pyenv 2> /dev/null; then
       # for testing, use the earliest point releases of the supported python versions:
-      pyenv global 3.5.3 3.6.8 3.7.0
-      pyenv local 3.5.3 3.6.8 3.7.0
+      pyenv global 3.5.3 3.6.9 3.7.0 3.8.0
+      pyenv local 3.5.3 3.6.9 3.7.0 3.8.0
     fi
     # otherwise: just use the system python
     if which fakeroot 2> /dev/null; then