make the ENABLE/DISABLE markers ASCII

notebook/nbextensions.py

@@ -35,8 +35,8 @@ from tornado.log import LogFormatter
 
 # Constants for pretty print extension listing function.
 # Window doesn't support unicode characters in the commandline, so use T/F.
-GREEN_ENABLED = '\033[32m✔️\033[0m' if os.name != 'nt' else 'T'
-RED_DISABLED = '\033[31m❌\033[0m' if os.name != 'nt' else 'F'
+GREEN_ENABLED = '\033[32mO\033[0m' if os.name != 'nt' else 'T'
+RED_DISABLED = '\033[31mX\033[0m' if os.name != 'nt' else 'F'
 
 #------------------------------------------------------------------------------
 # Public API