diff -r 1bb465fad209 -r 62855e1ce9d8 hgext3rd/topic/flow.py
--- a/hgext3rd/topic/flow.py	Wed Apr 08 01:16:57 2020 +0800
+++ b/hgext3rd/topic/flow.py	Fri May 08 20:36:32 2020 +0800
@@ -7,6 +7,7 @@
     extensions,
     node,
     phases,
+    util,
 )
 
 from mercurial.i18n import _
@@ -62,10 +63,18 @@
 
 def reject_publish(repo, tr):
     """prevent a transaction to be publish anything"""
-    published = set()
-    for r, (o, n) in tr.changes[b'phases'].items():
-        if n == phases.public:
-            published.add(r)
+    if util.safehasattr(tr.changes[b'phases'], 'items'):
+        # hg <= 5.3 (fdc802f29b2c)
+        published = {
+            r for r, (o, n) in tr.changes[b'phases'].items()
+            if n == phases.public
+        }
+    else:
+        revranges = [
+            r for r, (o, n) in tr.changes[b'phases']
+            if n == phases.public
+        ]
+        published = {r for revrange in revranges for r in revrange}
     if published:
         r = min(published)
         msg = b"rejecting publishing of changeset %s" % repo[r]
@@ -101,7 +110,8 @@
 
 def installpushflag(ui):
     entry = extensions.wrapcommand(commands.table, b'push', wrappush)
-    if not any(opt for opt in entry[1] if opt[1] == b'publish'): # hg <= 4.9
+    if not any(opt for opt in entry[1] if opt[1] == b'publish'):
+        # hg <= 4.8 (9b8d1ad851f8)
         entry[1].append((b'', b'publish', False,
                          _(b'push the changeset as public')))
     extensions.wrapfunction(exchange.pushoperation, '__init__',