hghave: byteify a path passed to a core API

hghave: byteify a path passed to a core API

It looks like this predicate isn't used at all(?)

--- a/tests/hghave.py	Mon Feb 27 18:24:29 2023 +0000
+++ b/tests/hghave.py	Tue Feb 28 11:41:50 2023 -0500
@@ -333,7 +333,7 @@
     fd, path = tempfile.mkstemp(dir='.', prefix=tempprefix)
     os.close(fd)
     try:
-        return util.cachestat(path).cacheable()
+        return util.cachestat(_sys2bytes(path)).cacheable()
     finally:
         os.remove(path)