Fix bug where open() was called even when COUNTY_BLOCK_FILE=None.

lib/bridgedb/Bucket.py

@@ -222,7 +222,7 @@ class BucketManager:
 
         # for a bridge, get the list of countries it might not work in
         blocklist = dict()
-        if hasattr(self.cfg, "COUNTRY_BLOCK_FILE"):
+        if getattr(self.cfg, "COUNTRY_BLOCK_FILE", None) is not None:
             f = open(self.cfg.COUNTRY_BLOCK_FILE, 'r')
             for ID,address,portlist,countries in bridgedb.Bridges.parseCountryBlockFile(f):
                 blocklist[toHex(ID)] = countries