Remove no_filenames string, and instead display CLI usage if you don't specify filenames

onionshare/__init__.py

@@ -67,7 +67,7 @@ def main(cwd=None):
 
     # Make sure filenames given if not using receiver mode
     if not receive and len(filenames) == 0:
-        print(strings._('no_filenames'))
+        parser.print_help()
         sys.exit()
 
     # Validate filenames

share/locale/en.json

@@ -8,7 +8,6 @@
     "ctrlc_to_stop":  "Press Ctrl+C to stop the server",
     "not_a_file": "{0:s} is not a valid file.",
     "not_a_readable_file": "{0:s} is not a readable file.",
-    "no_filenames": "You must specify a list of files to share.",
     "no_available_port": "Could not start the Onion service as there was no available port.",
     "other_page_loaded": "Address loaded",
     "close_on_timeout": "Stopped because timer expired",