Replace legacy error handling with exceptions

bdsh.py

@@ -45,22 +45,20 @@ def cmd_ld(self, args):
             items = os.listdir(dir)
             self.print('\t'.join([item + '/' if os.path.isdir(os.path.join(dir, item)) else item for item in items]))
         except FileNotFoundError:
-            self.print(f"{args[0]}: {args[1]}: does not exist")
+            raise FileNotFoundError(f"{args[1]}: does not exist")
 
     def cmd_def(self, args):
         if '-h' in args or '--help' in args:
             self.print(f"usage: def <keyword> <definition>{nl}binds <keyword> to <definition>{nl}executing <keyword> will execute <definition>")
             return
 
         if len(args) < 3:
-            self.print(f"def: missing params (at least 3)")
-            return
+            raise ValueError("missing params (at least 3)")
 
         definition = " ".join(args[2:])
 
         if args[1] == definition:
-            self.print(f"def: keyword cannot be the same as the definition")
-            return
+            raise SyntaxError("keyword cannot be the same as the definition")
 
         self.definitions[args[1]] = definition
         self.print(f"defined '{args[1]}' to run '{definition}'")