diff --git a/mercurial/debugcommands.py b/mercurial/debugcommands.py
--- a/mercurial/debugcommands.py
+++ b/mercurial/debugcommands.py
@@ -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
diff --git a/mercurial/formatter.py b/mercurial/formatter.py
--- a/mercurial/formatter.py
+++ b/mercurial/formatter.py
@@ -600,9 +600,9 @@
 
     # perhaps a stock style?
     if not os.path.split(tmpl)[0]:
-        (mapname, fp) = templater.open_template(
+        (mapname, fp) = templater.try_open_template(
             b'map-cmdline.' + tmpl
-        ) or templater.open_template(tmpl)
+        ) or templater.try_open_template(tmpl)
         if mapname:
             return mapfile_templatespec(topic, mapname, fp)
 
diff --git a/mercurial/hgweb/hgweb_mod.py b/mercurial/hgweb/hgweb_mod.py
--- a/mercurial/hgweb/hgweb_mod.py
+++ b/mercurial/hgweb/hgweb_mod.py
@@ -78,7 +78,7 @@
         locations = (os.path.join(style, b'map'), b'map-' + style, b'map')
 
         for location in locations:
-            mapfile, fp = templater.open_template(location, path)
+            mapfile, fp = templater.try_open_template(location, path)
             if mapfile:
                 return style, mapfile, fp
 
diff --git a/mercurial/logcmdutil.py b/mercurial/logcmdutil.py
--- a/mercurial/logcmdutil.py
+++ b/mercurial/logcmdutil.py
@@ -628,9 +628,9 @@
         mapfile = style
         fp = None
         if not os.path.split(mapfile)[0]:
-            (mapname, fp) = templater.open_template(
+            (mapname, fp) = templater.try_open_template(
                 b'map-cmdline.' + mapfile
-            ) or templater.open_template(mapfile)
+            ) or templater.try_open_template(mapfile)
             if mapname:
                 mapfile = mapname
         return formatter.mapfile_templatespec(b'changeset', mapfile, fp)
diff --git a/mercurial/templater.py b/mercurial/templater.py
--- a/mercurial/templater.py
+++ b/mercurial/templater.py
@@ -1095,17 +1095,18 @@
         templatepath = templatedir()
     if templatepath is not None or os.path.isabs(name):
         f = os.path.join(templatepath, name)
-        try:
-            return f, open(f, mode='rb')
-        except EnvironmentError:
-            return None, None
+        return f, open(f, mode='rb')
     else:
         name_parts = pycompat.sysstr(name).split('/')
         package_name = '.'.join(['mercurial', 'templates'] + name_parts[:-1])
-        try:
-            return (
-                name,
-                resourceutil.open_resource(package_name, name_parts[-1]),
-            )
-        except (ImportError, OSError):
-            return None, None
+        return (
+            name,
+            resourceutil.open_resource(package_name, name_parts[-1]),
+        )
+
+
+def try_open_template(name, templatepath=None):
+    try:
+        return open_template(name, templatepath)
+    except (EnvironmentError, ImportError):
+        return None, None