vagrant: use python 3.6.10 for binary build

Vagrantfile

@@ -134,7 +134,7 @@ def install_pythons(boxname)
     . ~/.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 3.6.9  # binary build, tests, version supporting openssl 1.1
+    pyenv install 3.6.10  # binary build, tests, version supporting openssl 1.1
     pyenv rehash
   EOF
 end
@@ -152,8 +152,8 @@ def build_pyenv_venv(boxname)
     . ~/.bash_profile
     cd /vagrant/borg
     # use the latest 3.6 release
-    pyenv global 3.6.9
-    pyenv virtualenv 3.6.9 borg-env
+    pyenv global 3.6.10
+    pyenv virtualenv 3.6.10 borg-env
     ln -s ~/.pyenv/versions/borg-env .
   EOF
 end
@@ -214,8 +214,8 @@ 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 3.6.9 3.7.0 3.8.0
-      pyenv local 3.6.9 3.7.0 3.8.0
+      pyenv global 3.6.10 3.7.0 3.8.0
+      pyenv local 3.6.10 3.7.0 3.8.0
     fi
     # otherwise: just use the system python
     if which fakeroot 2> /dev/null; then