compression: use sysstr to specify attribute to fetch for priority

These are attributes so they should be `str`.

mercurial/utils/compression.py

@@ -185,7 +185,7 b' class compressormanager:'
         """
         assert role in (SERVERROLE, CLIENTROLE)
 
-        attr = b'serverpriority' if role == SERVERROLE else b'clientpriority'
+        attr = 'serverpriority' if role == SERVERROLE else 'clientpriority'
 
         engines = [self._engines[e] for e in self._wiretypes.values()]
         if onlyavailable:

mercurial/wireprototypes.py

@@ -367,9 +367,7 b' def supportedcompengines(ui, role):'
     # No explicit config. Filter out the ones that aren't supposed to be
     # advertised and return default ordering.
     if not configengines:
-        attr = (
-            b'serverpriority' if role == util.SERVERROLE else b'clientpriority'
-        )
+        attr = 'serverpriority' if role == util.SERVERROLE else 'clientpriority'
         return [
             e for e in compengines if getattr(e.wireprotosupport(), attr) > 0
         ]