--- a/mercurial/pure/base85.py	Tue Nov 12 11:05:03 2019 +0100
+++ b/mercurial/pure/base85.py	Sat Nov 16 20:07:49 2019 +0100
@@ -67,7 +67,7 @@
                 acc = acc * 85 + _b85dec[c]
             except KeyError:
                 raise ValueError(
-                    b'bad base85 character at position %d' % (i + j)
+                    'bad base85 character at position %d' % (i + j)
                 )
         if acc > 4294967295:
             raise ValueError(b'Base85 overflow in hunk starting at byte %d' % i)