diff -r 42567ffa10a2 -r b29f490eb904 mercurial/hgweb/hgweb_mod.py
--- a/mercurial/hgweb/hgweb_mod.py	Fri Apr 13 22:33:38 2018 -0400
+++ b/mercurial/hgweb/hgweb_mod.py	Fri Apr 13 22:36:54 2018 -0400
@@ -208,7 +208,7 @@
     be multiple active threads inside __call__.
     """
     def __init__(self, repo, name=None, baseui=None):
-        if isinstance(repo, str):
+        if isinstance(repo, bytes):
             if baseui:
                 u = baseui.copy()
             else: