diff -r 8006fb8cdb77 -r 9bb00170780b tests/quadrilaterals.py
--- a/tests/quadrilaterals.py	Mon Jan 22 18:07:19 2018 +0200
+++ b/tests/quadrilaterals.py	Mon Jan 22 18:23:19 2018 +0200
@@ -1,4 +1,4 @@
-from math import acos, degrees, radians, pi as π
+from math import radians
 from testsuite import warning, error
 from geometry import *
 
@@ -36,8 +36,8 @@
     },
     'messages': {
         'skew-error': lambda skew_angle:
-            str.format('skew quadrilateral (plane angle {}°)',
-                '%.2f' % degrees(skew_angle),
+            str.format('skew quadrilateral (plane angle {})',
+                degree_rep(skew_angle),
             ),
         'concave-error': 'concave quadrilateral',
     },