From e5f4987a8fe1b2a1907436c11e0c5ae9ae6b12b3 Mon Sep 17 00:00:00 2001
From: stoned <stoned.elipot@gmail.com>
Date: Fri, 17 Aug 2018 21:11:43 +0200
Subject: [PATCH] Make mandatory filter error message more verbose (#44139)

...by adding the undefined variable/attribute name, if available.
---
 lib/ansible/plugins/filter/core.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/ansible/plugins/filter/core.py b/lib/ansible/plugins/filter/core.py
index 70d5b8cf52..0b9366ba92 100644
--- a/lib/ansible/plugins/filter/core.py
+++ b/lib/ansible/plugins/filter/core.py
@@ -299,7 +299,11 @@ def mandatory(a):
 
     ''' Make a variable mandatory '''
     if isinstance(a, Undefined):
-        raise AnsibleFilterError('Mandatory variable not defined.')
+        if a._undefined_name is not None:
+            name = "'%s' " % to_text(a._undefined_name)
+        else:
+            name = ''
+        raise AnsibleFilterError("Mandatory variable %snot defined." % name)
     return a