work around a python 27 incompatibility by defining FileNotFoundError

Author: marsmensch

bitcoin/rpc.py

@@ -42,6 +42,11 @@
 except ImportError:
     import urlparse
 
+try:
+    FileNotFoundError
+except NameError:
+    FileNotFoundError = IOError
+
 import bitcoin
 from bitcoin.core import COIN, x, lx, b2lx, CBlock, CBlockHeader, CTransaction, COutPoint, CTxOut
 from bitcoin.core.script import CScript