Don't crash if the urgencies file contains non-ascii

The live-2011-12-13 test set has random garbage in the middle.

Signed-off-by: Julien Cristau <jcristau@debian.org>

britney.py

@@ -783,7 +783,7 @@ class Britney(object):
         urgencies = {}
         filename = os.path.join(basedir, "Urgency")
         self.__log("Loading upload urgencies from %s" % filename)
-        for line in open(filename):
+        for line in open(filename, errors='surrogateescape'):
             l = line.split()
             if len(l) != 3: continue