push_notifications: Remove vestiges of base64 storage of tokens.

APNs tokens are provided by the client in hex, and we store them in
hex.  The existing code which attempts to "validate" them by parsing
them as base64 only works because base64 is a superset of hex.

Enforce that APNs tokens are hex, and remove all of the pieces of test
code which were incorrectly passing them in as base64 strings.

zerver/lib/push_notifications.py

@@ -1,7 +1,6 @@
 # See https://zulip.readthedocs.io/en/latest/subsystems/notifications.html
 
 import asyncio
-import base64
 import copy
 import logging
 import re
@@ -83,23 +82,13 @@ PUSH_REGISTRATION_LIVENESS_TIMEOUT = 24 * 60 * 60
 DeviceToken: TypeAlias = Union[PushDeviceToken, "RemotePushDeviceToken"]
 
 
-# We store the token as b64, but apns-client wants hex strings
-def b64_to_hex(data: str) -> str:
-    return base64.b64decode(data).hex()
-
-
-def hex_to_b64(data: str) -> str:
-    return base64.b64encode(bytes.fromhex(data)).decode()
-
-
 def validate_token(token_str: str, kind: int) -> None:
     if token_str == "" or len(token_str) > 4096:
         raise JsonableError(_("Empty or invalid length token"))
     if kind == PushDeviceToken.APNS:
-        # Validate that we can actually decode the token.
         try:
-            b64_to_hex(token_str)
-        except Exception:
+            bytes.fromhex(token_str)
+        except ValueError:
             raise JsonableError(_("Invalid APNS token"))