wrapfunction: use sysstr instead of bytes as argument in "sparse"

This is as valid and simpler, it will help us to eventually get ride of
`safehasattr`.

hgext/sparse.py

@@ -146,7 +146,7 b' def _setuplog(ui):'
             revs = revs.filter(ctxmatch)
         return revs
 
-    extensions.wrapfunction(logcmdutil, b'_initialrevs', _initialrevs)
+    extensions.wrapfunction(logcmdutil, '_initialrevs', _initialrevs)
 
 
 def _clonesparsecmd(orig, ui, repo, *args, **opts):
@@ -170,7 +170,7 b' def _clonesparsecmd(orig, ui, repo, *arg'
             )
             return orig(ctx, *args, **kwargs)
 
-        extensions.wrapfunction(mergemod, b'update', clonesparse)
+        extensions.wrapfunction(mergemod, 'update', clonesparse)
     return orig(ui, repo, *args, **opts)