diff -r 23c4ddda7bbe -r 34758397ad1b mercurial/lock.py
--- a/mercurial/lock.py	Fri Apr 13 12:50:47 2018 -0700
+++ b/mercurial/lock.py	Fri Apr 13 16:30:27 2018 +0530
@@ -348,7 +348,7 @@
         if self._parentheld:
             lockname = self.parentlock
         else:
-            lockname = '%s:%s' % (lock._host, self.pid)
+            lockname = b'%s:%d' % (lock._host, self.pid)
         self._inherited = True
         try:
             yield lockname