ledger: speed-up sign_transaction

really slow to scan usb devices for e.g. every tx input...
if user disconnects mid-signing, we would fail anyway.

electrum/plugins/ledger/ledger.py

@@ -351,7 +351,7 @@ class Ledger_KeyStore(Hardware_KeyStore):
         p2shTransaction = False
         segwitTransaction = False
         pin = ""
-        self.get_client() # prompt for the PIN before displaying the dialog if necessary
+        client_ledger = self.get_client() # prompt for the PIN before displaying the dialog if necessary
         client_electrum = self.get_client_electrum()
         assert client_electrum
 
@@ -450,13 +450,13 @@ class Ledger_KeyStore(Hardware_KeyStore):
                     redeemScripts.append(bfh(utxo[2]))
                 elif (not p2shTransaction) or client_electrum.supports_multi_output():
                     txtmp = bitcoinTransaction(bfh(utxo[0]))
-                    trustedInput = self.get_client().getTrustedInput(txtmp, utxo[1])
+                    trustedInput = client_ledger.getTrustedInput(txtmp, utxo[1])
                     trustedInput['sequence'] = sequence
                     if segwitTransaction:
                         trustedInput['witness'] = True
                     chipInputs.append(trustedInput)
                     if p2shTransaction or segwitTransaction:
-                        redeemScripts.append(bfh(utxo[2]))    
+                        redeemScripts.append(bfh(utxo[2]))
                     else:
                         redeemScripts.append(txtmp.outputs[utxo[1]].script)
                 else:
@@ -469,13 +469,13 @@ class Ledger_KeyStore(Hardware_KeyStore):
             firstTransaction = True
             inputIndex = 0
             rawTx = tx.serialize_to_network()
-            self.get_client().enableAlternate2fa(False)
+            client_ledger.enableAlternate2fa(False)
             if segwitTransaction:
-                self.get_client().startUntrustedTransaction(True, inputIndex,
+                client_ledger.startUntrustedTransaction(True, inputIndex,
                                                             chipInputs, redeemScripts[inputIndex], version=tx.version)
                 # we don't set meaningful outputAddress, amount and fees
                 # as we only care about the alternateEncoding==True branch
-                outputData = self.get_client().finalizeInput(b'', 0, 0, changePath, bfh(rawTx))
+                outputData = client_ledger.finalizeInput(b'', 0, 0, changePath, bfh(rawTx))
                 outputData['outputData'] = txOutput
                 if outputData['confirmationNeeded']:
                     outputData['address'] = output
@@ -486,9 +486,9 @@ class Ledger_KeyStore(Hardware_KeyStore):
                     self.handler.show_message(_("Confirmed. Signing Transaction..."))
                 while inputIndex < len(inputs):
                     singleInput = [ chipInputs[inputIndex] ]
-                    self.get_client().startUntrustedTransaction(False, 0,
+                    client_ledger.startUntrustedTransaction(False, 0,
                                                             singleInput, redeemScripts[inputIndex], version=tx.version)
-                    inputSignature = self.get_client().untrustedHashSign(inputsPaths[inputIndex], pin, lockTime=tx.locktime)
+                    inputSignature = client_ledger.untrustedHashSign(inputsPaths[inputIndex], pin, lockTime=tx.locktime)
                     inputSignature[0] = 0x30 # force for 1.4.9+
                     my_pubkey = inputs[inputIndex][4]
                     tx.add_signature_to_txin(txin_idx=inputIndex,
@@ -497,11 +497,11 @@ class Ledger_KeyStore(Hardware_KeyStore):
                     inputIndex = inputIndex + 1
             else:
                 while inputIndex < len(inputs):
-                    self.get_client().startUntrustedTransaction(firstTransaction, inputIndex,
+                    client_ledger.startUntrustedTransaction(firstTransaction, inputIndex,
                                                                 chipInputs, redeemScripts[inputIndex], version=tx.version)
                     # we don't set meaningful outputAddress, amount and fees
                     # as we only care about the alternateEncoding==True branch
-                    outputData = self.get_client().finalizeInput(b'', 0, 0, changePath, bfh(rawTx))
+                    outputData = client_ledger.finalizeInput(b'', 0, 0, changePath, bfh(rawTx))
                     outputData['outputData'] = txOutput
                     if outputData['confirmationNeeded']:
                         outputData['address'] = output
@@ -512,7 +512,7 @@ class Ledger_KeyStore(Hardware_KeyStore):
                         self.handler.show_message(_("Confirmed. Signing Transaction..."))
                     else:
                         # Sign input with the provided PIN
-                        inputSignature = self.get_client().untrustedHashSign(inputsPaths[inputIndex], pin, lockTime=tx.locktime)
+                        inputSignature = client_ledger.untrustedHashSign(inputsPaths[inputIndex], pin, lockTime=tx.locktime)
                         inputSignature[0] = 0x30 # force for 1.4.9+
                         my_pubkey = inputs[inputIndex][4]
                         tx.add_signature_to_txin(txin_idx=inputIndex,