fix imports in hardware wallets

plugins/ledger/ledger.py

@@ -496,7 +496,7 @@ class LedgerPlugin(BasePlugin):
             tx.error = str(e)
 
 
-class CmdlinePlugin(Plugin):
+class CmdlinePlugin(LedgerPlugin):
     @hook
     def cmdline_load_wallet(self, wallet):
         self.wallet = wallet

plugins/ledger/qt.py

@@ -1,6 +1,10 @@
 from PyQt4.Qt import QApplication, QMessageBox, QDialog, QInputDialog, QLineEdit, QVBoxLayout, QLabel, QThread, SIGNAL
 import PyQt4.QtCore as QtCore
+
 from electrum_gui.qt.password_dialog import make_password_dialog, run_password_dialog
+from electrum.plugins import BasePlugin, hook
+
+from ledger import LedgerPlugin
 
 class Plugin(LedgerPlugin):