Prefer Python 3 executables over python 2 during install

get-poetry.py

@@ -638,7 +638,7 @@ class Installer:
 
     def _which_python(self):
         """Decides which python executable we'll embed in the launcher script."""
-        allowed_executables = ["python", "python3"]
+        allowed_executables = ["python3", "python"]
         if WINDOWS:
             allowed_executables += ["py.exe -3", "py.exe -2"]