fix: add simple rendering logic for currency values and errors

tests/test_util.py

@@ -317,3 +317,20 @@ class TestResourcePath(TestCase):
 
             # absolute path returned as-is
             self.assertEqual(mod.resource_path('/tmp/doesnotexist.txt'), '/tmp/doesnotexist.txt')
+
+
+class TestSimpleError(TestCase):
+
+    def test_with_description(self):
+        try:
+            raise RuntimeError("just testin")
+        except Exception as error:
+            result = mod.simple_error(error)
+        self.assertEqual(result, "RuntimeError: just testin")
+
+    def test_without_description(self):
+        try:
+            raise RuntimeError
+        except Exception as error:
+            result = mod.simple_error(error)
+        self.assertEqual(result, "RuntimeError")