protocol.py: Silence web server INFO if running without UI

Testing the outfitting.py changes brought this to light.  I know, e.g.
TCE that uses EDMC.exe likes to have no extraneous output.

protocol.py

@@ -1,5 +1,6 @@
 """protocol handler for cAPI authorisation."""
 
+import os
 import sys
 import threading
 import urllib.error
@@ -336,7 +337,9 @@ else:  # Linux / Run from source
             super().__init__()
             self.httpd = HTTPServer(('localhost', 0), HTTPRequestHandler)
             self.redirect = f'http://localhost:{self.httpd.server_port}/auth'
-            logger.info(f'Web server listening on {self.redirect}')
+            if not os.getenv("EDMC_NO_UI"):
+                logger.info(f'Web server listening on {self.redirect}')
+
             self.thread: Optional[threading.Thread] = None
 
         def start(self, master) -> None: