fix #2562: show error message if hardware library is missing

plugins/hw_wallet/plugin.py

@@ -41,7 +41,7 @@ class HW_PluginBase(BasePlugin):
         self.keystore_class.plugin = self
 
     def is_enabled(self):
-        return self.libraries_available
+        return True
 
     def device_manager(self):
         return self.parent.device_manager

plugins/hw_wallet/qt.py

@@ -182,6 +182,12 @@ class QtPluginBase(object):
         for keystore in wallet.get_keystores():
             if not isinstance(keystore, self.keystore_class):
                 continue
+            if not self.libraries_available:
+                window.show_error(
+                    _("Cannot find python library for") + " '%s'.\n" % self.name \
+                    + _("Make sure you install it with python3")
+                )
+                return
             tooltip = self.device + '\n' + (keystore.label or 'unnamed')
             cb = partial(self.show_settings_dialog, window, keystore)
             button = StatusBarButton(QIcon(self.icon_unpaired), tooltip, cb)