From b15f3b9b0e395982870711de8ff0d373259ade1f Mon Sep 17 00:00:00 2001
From: jMyles <justin@justinholmes.com>
Date: Thu, 8 Feb 2018 11:30:24 -0800
Subject: [PATCH] Raise class-scoped error instead of RuntimeError.

---
 umbral/config.py | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/umbral/config.py b/umbral/config.py
index a3cbc91..8c66abb 100644
--- a/umbral/config.py
+++ b/umbral/config.py
@@ -5,24 +5,27 @@ class _CONFIG:
     __curve = None
     __params = None
 
+    class UmbralConfigurationError(RuntimeError):
+        """Raised when somebody does something dumb re: configuration."""
+
     @classmethod
     def params(cls):
         if not cls.__params:
-            raise RuntimeError("No default curve has been set; you need one for default params.")
+            raise cls.UmbralConfigurationError("No default curve has been set; you need one for default params.")
         else:
             return cls.__params
 
     @classmethod
     def curve(cls):
         if not cls.__curve:
-            raise RuntimeError("No default curve has been set.")
+            raise cls.UmbralConfigurationError("No default curve has been set.")
         else:
             return cls.__curve
 
     @classmethod
     def set_curve(cls, curve: ec.EllipticCurve=None):
         if cls.__curve:
-            raise RuntimeError("You can only set the default curve once.  Do it once and then leave it alone.")
+            raise cls.UmbralConfigurationError("You can only set the default curve once.  Do it once and then leave it alone.")
         else:
             from umbral.params import UmbralParameters
             cls.__curve = curve