Merge pull request #1091 from drizzt/patch-1

Remove useless enforced dependency of PyUSB

plugins/btchipwallet.py

@@ -20,7 +20,6 @@ from electrum.util import format_satoshis
 import hashlib
 
 try:
-    from usb.core import USBError
     from btchip.btchipComm import getDongle, DongleWait
     from btchip.btchip import btchip
     from btchip.btchipUtils import compress_public_key,format_transaction, get_regular_input_script