silence stdout on prune

trueupdate/__init__.py

@@ -112,10 +112,7 @@ def docker_prune():
     if PRUNE:
       print("Pruning old docker images...\n")
       process = subprocess.Popen(["docker", "image", "prune", "-af"], stdout=subprocess.PIPE)
-      while process.poll() is None:
-          lines = process.stdout.readline()
-          print (lines)
-      print (process.stdout.read())
+      print("Images pruned.\n")
   
 def run():
     process_args()