Python 3.13 compatibility

[Daft-Freak]

Trying to run on python 3.13 results in:

[...]
    @app.get(f'/<any({",".join(PROTOCOLS)}):protocol>/<id>')
                      ~~~~~~~~^^^^^^^^^^^
TypeError: sequence item 12: expected str instance, method found

Where item 12 is:

<bound method LABEL of Web<...>: Web<...>

Which I think is because Protocol.LABEL is a class property and those were removed in 3.13.

[snarfed]

Ooh, thanks for filing! Bridgy Fed currently runs on Python 3.12, but this is useful to know.

[Daft-Freak]

Blew up my local setup pretty fast, ended up working around it with this:

diff --git a/protocol.py b/protocol.py
index 25135da1..6e210b61 100644
--- a/protocol.py
+++ b/protocol.py
@@ -90,6 +90,13 @@ werkzeug.exceptions._aborter.mapping.setdefault(299, ErrorButDoNotRetryTask)
 def activity_id_memcache_key(id):
     return memcache.key(f'receive-{id}')
 
+class classproperty:
+    def __init__(self, method):
+        self.method = method
+    def __get__(self, obj, cls=None):
+        if cls is None:
+            cls = type(obj)
+        return self.method(cls)
 
 class Protocol:
     """Base protocol class. Not to be instantiated; classmethods only."""
@@ -123,8 +130,7 @@ class Protocol:
     def __init__(self):
         assert False
 
-    @classmethod
-    @property
+    @classproperty
     def LABEL(cls):
         """str: human-readable lower case name of this protocol, eg ``'activitypub``"""
         return cls.__name__.lower()