diff -r 15c998528c36 -r 21fa3d3688f3 mercurial/debugcommands.py
--- a/mercurial/debugcommands.py	Tue Mar 07 12:52:00 2017 -0800
+++ b/mercurial/debugcommands.py	Thu Mar 02 03:52:36 2017 +0100
@@ -76,7 +76,7 @@
     """find the ancestor revision of two revisions in a given index"""
     if len(args) == 3:
         index, rev1, rev2 = args
-        r = revlog.revlog(scmutil.opener(pycompat.getcwd(), audit=False), index)
+        r = revlog.revlog(scmutil.vfs(pycompat.getcwd(), audit=False), index)
         lookup = r.lookup
     elif len(args) == 2:
         if not repo:
@@ -452,7 +452,7 @@
     spaces = opts.get('spaces')
     dots = opts.get('dots')
     if file_:
-        rlog = revlog.revlog(scmutil.opener(pycompat.getcwd(), audit=False),
+        rlog = revlog.revlog(scmutil.vfs(pycompat.getcwd(), audit=False),
                              file_)
         revs = set((int(r) for r in revs))
         def events():