HW_PluginBase: small clean-up for 'maximum_library'

electrum/plugins/hw_wallet/plugin.py

@@ -46,7 +46,9 @@ class HW_PluginBase(BasePlugin):
     keystore_class: Type['Hardware_KeyStore']
     libraries_available: bool
 
+    # define supported library versions:  minimum_library <= x < maximum_library
     minimum_library = (0, )
+    maximum_library = (float('inf'), )
 
     def __init__(self, parent, config, name):
         BasePlugin.__init__(self, parent, config, name)
@@ -149,17 +151,16 @@ class HW_PluginBase(BasePlugin):
             # if no exception so far, we might still raise LibraryFoundButUnusable
             if (library_version == 'unknown'
                     or versiontuple(library_version) < self.minimum_library
-                    or hasattr(self, "maximum_library") and versiontuple(library_version) >= self.maximum_library):
+                    or versiontuple(library_version) >= self.maximum_library):
                 raise LibraryFoundButUnusable(library_version=library_version)
         except ImportError:
             return False
         except LibraryFoundButUnusable as e:
             library_version = e.library_version
-            max_version_str = version_str(self.maximum_library) if hasattr(self, "maximum_library") else "inf"
             self.libraries_available_message = (
                     _("Library version for '{}' is incompatible.").format(self.name)
                     + '\nInstalled: {}, Needed: {} <= x < {}'
-                    .format(library_version, version_str(self.minimum_library), max_version_str))
+                    .format(library_version, version_str(self.minimum_library), version_str(self.maximum_library)))
             self.logger.warning(self.libraries_available_message)
             return False