diff -r 37ef6ee87488 -r 242eb5132203 mercurial/hook.py
--- a/mercurial/hook.py	Sun May 13 11:09:53 2018 +0900
+++ b/mercurial/hook.py	Wed May 16 14:11:41 2018 -0600
@@ -24,7 +24,7 @@
     stringutil,
 )
 
-def _pythonhook(ui, repo, htype, hname, funcname, args, throw):
+def pythonhook(ui, repo, htype, hname, funcname, args, throw):
     '''call python hook. hook is callable object, looked up as
     name in python module. if callable returns "true", hook
     fails, else passes. if hook raises exception, treated as
@@ -242,7 +242,7 @@
                 r = 1
                 raised = False
             elif callable(cmd):
-                r, raised = _pythonhook(ui, repo, htype, hname, cmd, args,
+                r, raised = pythonhook(ui, repo, htype, hname, cmd, args,
                                         throw)
             elif cmd.startswith('python:'):
                 if cmd.count(':') >= 2:
@@ -258,7 +258,7 @@
                     hookfn = getattr(mod, cmd)
                 else:
                     hookfn = cmd[7:].strip()
-                r, raised = _pythonhook(ui, repo, htype, hname, hookfn, args,
+                r, raised = pythonhook(ui, repo, htype, hname, hookfn, args,
                                         throw)
             else:
                 r = _exthook(ui, repo, htype, hname, cmd, args, throw)