From 5fef1e7980e6c9811448ad7d9fb6afa4460ac7fc Mon Sep 17 00:00:00 2001
From: SomberNight <somber.night@protonmail.com>
Date: Mon, 19 Mar 2018 01:26:57 +0100
Subject: [PATCH] close #4125

perhaps not proper fix but at least more descriptive exception text
---
 lib/blockchain.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/blockchain.py b/lib/blockchain.py
index f6fe31dcf..cf516069a 100644
--- a/lib/blockchain.py
+++ b/lib/blockchain.py
@@ -255,6 +255,10 @@ class Blockchain(util.PrintError):
             with open(name, 'rb') as f:
                 f.seek(delta * 80)
                 h = f.read(80)
+        elif not os.path.exists(util.get_headers_dir(self.config)):
+            raise Exception('Electrum datadir does not exist. Was it deleted while running?')
+        else:
+            raise Exception('Cannot find headers file but datadir is there. Should be at {}'.format(name))
         if h == bytes([0])*80:
             return None
         return deserialize_header(h, height)