From 072e4728079e6caf521339e3934e1279aa09e83d Mon Sep 17 00:00:00 2001
From: "Edward Z. Yang" <ezyang@cs.stanford.edu>
Date: Mon, 28 Dec 2015 18:42:45 -0800
Subject: [PATCH] Try to give a more helpful error message when we can't read
 LBI.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>
---
 Cabal/tests/PackageTests.hs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Cabal/tests/PackageTests.hs b/Cabal/tests/PackageTests.hs
index 3ac9f6e2b9..3b45813093 100644
--- a/Cabal/tests/PackageTests.hs
+++ b/Cabal/tests/PackageTests.hs
@@ -210,6 +210,10 @@ getPersistBuildConfig_ filename = do
     eLBI <- try $ getConfigStateFile filename
     case eLBI of
       Left (ConfigStateFileBadVersion _ _ (Right lbi)) -> return lbi
-      Left (ConfigStateFileBadVersion _ _ (Left err)) -> throw err
+      Left (ConfigStateFileBadVersion _ _ (Left err))
+        -> error $ "We couldn't understand the build configuration.  Try " ++
+                   "building Cabal with a more recent version of itself " ++
+                   "and then running the test suite.\n\nOriginal error: " ++
+                   show err
       Left err -> throw err
       Right lbi -> return lbi
-- 
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