api: remove authentication fallback for pre-0.12 proxies

passbook/api/auth.py

@@ -25,10 +25,7 @@ def token_from_header(raw_header: bytes) -> Optional[Token]:
     try:
         auth_credentials = b64decode(auth_credentials.encode()).decode()
     except UnicodeDecodeError:
-        # TODO: Remove this workaround
-        # temporary fallback for 0.11 to 0.12 upgrade
-        # 0.11 and below proxy sends authorization header not base64 encoded
-        pass
+        return None
     # Accept credentials with username and without
     if ":" in auth_credentials:
         _, password = auth_credentials.split(":")