diff -r 6e6fe826ba69 -r 4aa484efc926 mercurial/debugcommands.py
--- a/mercurial/debugcommands.py	Wed Aug 05 22:13:51 2020 -0700
+++ b/mercurial/debugcommands.py	Thu Aug 06 09:50:10 2020 -0700
@@ -1672,7 +1672,7 @@
     fm.write(b'templatedirs', b'checking templates (%s)...\n', p or b'')
     fm.condwrite(not p, b'', _(b" no template directories found\n"))
     if p:
-        (m, fp) = templater.open_template(b"map-cmdline.default")
+        (m, fp) = templater.try_open_template(b"map-cmdline.default")
         if m:
             # template found, check if it is working
             err = None