qt: handle expected errors in DSCancelDialog

closes https://github.com/spesmilo/electrum/issues/8390

electrum/gui/qt/rbf_dialog.py

@@ -15,7 +15,7 @@ from .util import (ColorScheme, WindowModalDialog, Buttons,
 
 from electrum.i18n import _
 from electrum.transaction import PartialTransaction
-from electrum.wallet import CannotBumpFee
+from electrum.wallet import CannotRBFTx
 
 if TYPE_CHECKING:
     from .main_window import ElectrumWindow
@@ -124,7 +124,7 @@ class _BaseRBFDialog(TxEditor):
         else:
             try:
                 self.tx = self.make_tx(fee_rate)
-            except CannotBumpFee as e:
+            except CannotRBFTx as e:
                 self.tx = None
                 self.error = str(e)
 

electrum/wallet.py

@@ -225,12 +225,14 @@ def get_locktime_for_new_transaction(network: 'Network') -> int:
     return locktime
 
 
+class CannotRBFTx(Exception): pass
 
-class CannotBumpFee(Exception):
+
+class CannotBumpFee(CannotRBFTx):
     def __str__(self):
         return _('Cannot bump fee') + ':\n\n' + Exception.__str__(self)
 
-class CannotDoubleSpendTx(Exception):
+class CannotDoubleSpendTx(CannotRBFTx):
     def __str__(self):
         return _('Cannot cancel transaction') + ':\n\n' + Exception.__str__(self)