From d256d4ec2c73b035cb060d30f957fc255c3a444c Mon Sep 17 00:00:00 2001
From: Michael Krayer <michael.krayer@posteo.de>
Date: Thu, 3 Jun 2021 12:48:43 +0200
Subject: [PATCH] output rel_shift if assertion false

---
 field.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/field.py b/field.py
index a9dfb30..b60af87 100644
--- a/field.py
+++ b/field.py
@@ -371,7 +371,7 @@ class Field3d:
         assert isinstance(rel_shift,(tuple,list,numpy.ndarray)) and len(rel_shift)==3,\
             "'shift' must be tuple/list with length 3."
         assert all([rel_shift[ii]>=-1.0 and rel_shift[ii]<=1.0 for ii in range(3)]),\
-            "'shift' must be in (-1.0,1.0)."
+            "'shift' must be in (-1.0,1.0). {}".format(rel_shift)
         data = self.data.copy()
         origin = list(self.origin)
         sl = 3*[slice(None)]