Handy new class PrintError

Saves adding "def print_error" to endless classes.

lib/blockchain.py

@@ -22,7 +22,7 @@ import util
 from bitcoin import *
 
 
-class Blockchain():
+class Blockchain(util.PrintError):
     '''Manages blockchain headers and their verification'''
     def __init__(self, config, network):
         self.config = config
@@ -31,9 +31,6 @@ class Blockchain():
         self.local_height = 0
         self.set_local_height()
 
-    def print_error(self, *msg):
-        util.print_error("[blockchain]", *msg)
-
     def height(self):
         return self.local_height