QT install wizard: catch general exceptions

and show an error before re-raising and exiting.  Improvement on
prior.

gui/qt/installwizard.py

@@ -166,6 +166,9 @@ class InstallWizard(QDialog, MessageBoxMixin, WizardBase):
         except UserCancelled:
             self.print_error("wallet creation cancelled by user")
             self.accept()  # For when called from menu
+        except BaseException as e:
+            self.show_error(str(e))
+            raise
         return wallet
 
     def remove_from_recently_open(self, filename):

plugins/trezor/plugin.py

@@ -221,8 +221,7 @@ class TrezorCompatiblePlugin(HW_PluginBase):
         devmgr = self.device_manager()
         device_info = devmgr.select_device(wallet, self)
         if not device_info:
-            wallet.handler.show_error(_("No devices found"))
-            raise RuntimeError("No devices found")
+            raise RuntimeError(_("No devices found"))
         devmgr.pair_wallet(wallet, device_info.device.id_)
         if device_info.initialized:
             task = partial(wallet.create_hd_account, None)