some gui checking

Gui.py

@@ -464,6 +464,12 @@ def guiMain(args=None):
             elif type(v) is dict: # use same settings for every player
                 setattr(guiargs, k, {player: getattr(guiargs, k) for player in range(1, guiargs.multi + 1)})
         try:
+            if not guiargs.suppress_rom:
+                if not os.path.exists(guiargs.rom):
+                    raise FileNotFoundError(f"Could not find specified rom file {guiargs.rom}")
+                else:
+                    import Patch
+                    Patch.get_base_rom_bytes(guiargs.rom)  # throws error on checksum fail
             if guiargs.count is not None:
                 seed = guiargs.seed
                 for _ in range(guiargs.count):

Patch.py

@@ -3,7 +3,7 @@ import yaml
 import os
 import lzma
 import hashlib
-from typing import Tuple
+from typing import Tuple, Optional
 
 import Utils
 from Rom import JAP10HASH, read_rom
@@ -11,11 +11,12 @@ from Rom import JAP10HASH, read_rom
 base_rom_bytes = None
 
 
-def get_base_rom_bytes() -> bytes:
+def get_base_rom_bytes(file_name: str = None) -> bytes:
     global base_rom_bytes
     if not base_rom_bytes:
         options = Utils.get_options()
-        file_name = options["general_options"]["rom_file"]
+        if not file_name:
+            file_name = options["general_options"]["rom_file"]
         if not os.path.exists(file_name):
             file_name = Utils.local_path(file_name)
         base_rom_bytes = bytes(read_rom(open(file_name, "rb")))