move import test to wallet.py

lib/commands.py

@@ -277,7 +277,6 @@ 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

lib/wallet.py

@@ -288,6 +288,7 @@ class Abstract_Wallet(object):
         return account is not None
 
     def import_key(self, sec, password):
+        assert self.can_import()
         try:
             pubkey = public_key_from_private_key(sec)
             address = public_key_to_bc_address(pubkey.decode('hex'))