add check in importprivkey

lib/commands.py

@@ -277,6 +277,7 @@ class Commands:
         return s.encode('utf8')
 
     def importprivkey(self, sec):
+        assert self.wallet.can_import()
         try:
             addr = self.wallet.import_key(sec,self.password)
             out = "Keypair imported: ", addr