diff -r 223296268c4e -r ed0ded64a8a9 mercurial/merge.py
--- a/mercurial/merge.py	Fri Oct 09 08:08:54 2020 -0700
+++ b/mercurial/merge.py	Fri Oct 09 09:17:47 2020 -0700
@@ -1309,7 +1309,8 @@
             wctx[f].remove(ignoremissing=True)
         except OSError as inst:
             repo.ui.warn(
-                _(b"update failed to remove %s: %s!\n") % (f, inst.strerror)
+                _(b"update failed to remove %s: %s!\n")
+                % (f, pycompat.bytestr(inst.strerror))
             )
         if i == 100:
             yield i, f