diff -r f99d64e8a4e4 -r f0b6fbea00cf mercurial/revlog.py
--- a/mercurial/revlog.py	Thu Mar 22 21:19:31 2018 +0900
+++ b/mercurial/revlog.py	Thu Mar 22 21:56:20 2018 +0900
@@ -45,6 +45,9 @@
     templatefilters,
     util,
 )
+from .utils import (
+    stringutil,
+)
 
 parsers = policy.importmod(r'parsers')
 
@@ -2017,7 +2020,7 @@
                 return _zlibdecompress(data)
             except zlib.error as e:
                 raise RevlogError(_('revlog decompress error: %s') %
-                                  util.forcebytestr(e))
+                                  stringutil.forcebytestr(e))
         # '\0' is more common than 'u' so it goes first.
         elif t == '\0':
             return data