Refactor "try" block in read_cartridge.

Remove custom exception Read_error in favor of standard Failure.

src/cartridge.ml

@@ -3,7 +3,6 @@ open Printf
 
 (** http://bgb.bircd.org/pandocs.htm#thecartridgeheader *)
 
-exception Read_error
 
 type memory_bank_controller =
   | ROM_ONLY
@@ -41,7 +40,7 @@ let get_ROM_size = function
   | 0x52 -> 1100 (* 72 banks *)
   | 0x53 -> 1200 (* 80 banks *)
   | 0x54 -> 1500 (* 96 banks *)
-  | _ -> raise Read_error
+  | _ -> failwith "Invalid ROM size code."
 
 (** RAM size is expressed in KB *)
 let get_RAM_size = function
@@ -49,7 +48,7 @@ let get_RAM_size = function
   | 0x01 -> 2
   | 0x02 -> 8
   | 0x03 -> 32 (* 4 x 8KB banks *)
-  | _ -> raise Read_error
+  | _ -> failwith "Invalid RAM size code."
 
 
 let read_cartridge file =
@@ -62,8 +61,6 @@ let read_cartridge file =
     really_input ic full_rom 0 file_size;
     close_in ic;
 
-    try
-
       (* Nintendo logo *)
       let nin_logo_offset = 0x0104 in
       let nin_logo_size = 48 in
@@ -85,8 +82,7 @@ let read_cartridge file =
 
       Some { full_rom; nintendo_logo; title; rom_size; ram_size }
 
-    with
-    | Invalid_argument(msg) -> None (* This is triggered by Bytes.sub *)
-    | Read_error -> None
-
-  with Sys_error(msg) -> None
+  with
+  | Sys_error msg
+  | Invalid_argument msg (* This is triggered by Bytes.sub *)
+  | Failure msg -> prerr_endline msg; None