--- a/hgext3rd/topic/compat.py	Fri Jul 12 23:24:04 2019 -0700
+++ b/hgext3rd/topic/compat.py	Sat Jul 13 00:17:03 2019 -0700
@@ -9,6 +9,7 @@
 
 from mercurial import (
     obsolete,
+    pycompat,
 )
 
 getmarkers = None
@@ -24,3 +25,10 @@
     getmarkers = obsolete.getmarkers
 if successorssets is None:
     successorssets = obsolete.successorssets
+
+if pycompat.ispy3:
+    def branchmapitems(branchmap):
+        return branchmap.items()
+else:
+    def branchmapitems(branchmap):
+        return branchmap.iteritems()

--- a/hgext3rd/topic/discovery.py	Fri Jul 12 23:24:04 2019 -0700
+++ b/hgext3rd/topic/discovery.py	Sat Jul 13 00:17:03 2019 -0700
@@ -14,6 +14,7 @@
 )
 from . import (
     common,
+    compat,
 )
 
 try:
@@ -49,7 +50,7 @@
     def remotebranchmap():
         # drop topic information from changeset about to be published
         result = collections.defaultdict(list)
-        for branch, heads in origremotebranchmap().iteritems():
+        for branch, heads in compat.branchmapitems(origremotebranchmap()):
             if ':' not in branch:
                 result[branch].extend(heads)
             else:

--- a/hgext3rd/topic/flow.py	Fri Jul 12 23:24:04 2019 -0700
+++ b/hgext3rd/topic/flow.py	Sat Jul 13 00:17:03 2019 -0700
@@ -11,8 +11,13 @@
 
 from mercurial.i18n import _
 
+from . import (
+    compat,
+)
+
 def enforcesinglehead(repo, tr):
-    for name, heads in repo.filtered('visible').branchmap().iteritems():
+    branchmap = repo.filtered('visible').branchmap()
+    for name, heads in compat.branchmapitems(branchmap):
         if len(heads) > 1:
             hexs = [node.short(n) for n in heads]
             raise error.Abort(_('%d heads on "%s"') % (len(heads), name),