use pyinstaller 4.7

Vagrantfile

@@ -205,7 +205,7 @@ def install_pyinstaller()
     . borg-env/bin/activate
     git clone https://github.com/thomaswaldmann/pyinstaller.git
     cd pyinstaller
-    git checkout v4.3-maint
+    git checkout v4.7-maint
     python setup.py install
   EOF
 end