update venv command

pythonbrew/util.py

@@ -221,6 +221,10 @@ def get_using_python_pkgname():
             return d
     return None
 
+def get_installed_pythons_pkgname():
+    """Get the installed python versions list."""
+    return [d for d in sorted(os.listdir(PATH_PYTHONS))]
+
 def is_installed(name):
     pkgname = Package(name).name
     pkgdir = os.path.join(PATH_PYTHONS, pkgname)