use python 3.5.1 to build binaries

Vagrantfile

@@ -160,7 +160,7 @@ def install_pythons(boxname)
     pyenv install 3.3.0  # tests
     pyenv install 3.4.0  # tests
     pyenv install 3.5.0  # tests
-    #pyenv install 3.5.1  # binary build, use latest 3.5.x release
+    pyenv install 3.5.1  # binary build, use latest 3.5.x release
     pyenv rehash
   EOF
 end
@@ -178,8 +178,8 @@ def build_pyenv_venv(boxname)
     . ~/.bash_profile
     cd /vagrant/borg
     # use the latest 3.5 release
-    pyenv global 3.5.0
-    pyenv virtualenv 3.5.0 borg-env
+    pyenv global 3.5.1
+    pyenv virtualenv 3.5.1 borg-env
     ln -s ~/.pyenv/versions/borg-env .
   EOF
 end