[BTC Language] Raise an error when an invalid opcode is encountered.

symbolic_execution/language/bitcoin/op_codes.py

@@ -2,6 +2,7 @@
 import hashlib
 import operator
 from typing import Any, Callable, Dict, List
+from symbolic_execution.language.exceptions import InvalidOpCode
 from symbolic_execution.program.instruction.general import (
     NOP,
     InvalidInstruction,
@@ -787,7 +788,7 @@ class OpCodes:
         if opcode in OpCodes.__int_to_tokens:
             return OpCodes.__int_to_tokens[opcode]
         else:
-            return None
+            raise InvalidOpCode(f"No known token for {opcode}")
 
     def token_to_opcode(token: str) -> OpCode:
         """Return the Opcode (object) associated to a token."""

symbolic_execution/language/bitcoin/parser.py

@@ -51,11 +51,10 @@ class BitcoinParser(ILanguage):
         # The only difference with a BYTE, is that an OP_CODE needs to be
         # converted into a token.
         OP_CODE = Word(hexnums, exact=2)
-        OP_CODE.addParseAction(
-            lambda tokens: list(
-                map(lambda t: OpCodes.int_to_tokens(int(t, 16)), tokens)
-            )
-        )
+
+        @OP_CODE.addParseAction
+        def tokenify(tokens):
+            return list(map(lambda t: OpCodes.int_to_tokens(int(t, 16)), tokens))
 
         # CONSTANTS
         OP_PUSH_0 = Or([format(op, "02x") for op in range(0x01, 0x4C)])

symbolic_execution/language/exceptions.py

+"""Custom exception for language."""
+
+
+class InvalidOpCode(Exception):
+    """Raised when attempting to tokenify an unknown opcode."""
+
+    def __init__(self, message: str):
+        """Init the exception."""
+        super().__init__(message)