core/bitcoin: Move BIP32_WALLET_DEPTH to common.

core/src/apps/bitcoin/common.py

@@ -18,6 +18,9 @@ BITCOIN_NAMES = ("Bitcoin", "Regtest", "Testnet")
 # Default signature hash type in Bitcoin which signs all inputs and all outputs of the transaction.
 SIGHASH_ALL = const(0x01)
 
+# The number of bip32 levels used in a wallet (chain and address)
+BIP32_WALLET_DEPTH = const(2)
+
 # supported witness version for bech32 addresses
 _BECH32_WITVER = const(0x00)
 

core/src/apps/bitcoin/sign_tx/matchcheck.py

@@ -1,18 +1,14 @@
-from micropython import const
-
 from trezor import wire
 from trezor.messages.TxInputType import TxInputType
 from trezor.messages.TxOutputType import TxOutputType
 from trezor.utils import ensure
 
 from .. import multisig
+from ..common import BIP32_WALLET_DEPTH
 
 if False:
     from typing import Any, Union
 
-# the number of bip32 levels used in a wallet (chain and address)
-_BIP32_WALLET_DEPTH = const(2)
-
 
 class MatchChecker:
     """
@@ -85,7 +81,7 @@ class WalletPathChecker(MatchChecker):
     def attribute_from_tx(self, txio: Union[TxInputType, TxOutputType]) -> Any:
         if not txio.address_n:
             return None
-        return txio.address_n[:-_BIP32_WALLET_DEPTH]
+        return txio.address_n[:-BIP32_WALLET_DEPTH]
 
 
 class MultisigFingerprintChecker(MatchChecker):