Update caremap to by py3 compatible

Py3 doesn't mix bytes/str, so be explicit about which one

Test: th
Change-Id: Ia091b8378da93f19c3eb7c944199163aa9c63de7
diff --git a/update_verifier/care_map_generator.py b/update_verifier/care_map_generator.py
index c6f2dad..b1396a4 100644
--- a/update_verifier/care_map_generator.py
+++ b/update_verifier/care_map_generator.py
@@ -111,14 +111,14 @@
   logging.basicConfig(level=logging.INFO if args.verbose else logging.WARNING,
                       format=logging_format)
 
-  with open(args.input_care_map, 'r') as input_care_map:
+  with open(args.input_care_map, 'rb') as input_care_map:
     content = input_care_map.read()
 
   if args.parse_proto:
     result = ParseProtoMessage(content, args.fingerprint_enabled).encode()
   else:
     care_map_proto = GenerateCareMapProtoFromLegacyFormat(
-        content.rstrip().splitlines(), args.fingerprint_enabled)
+        content.decode().rstrip().splitlines(), args.fingerprint_enabled)
     result = care_map_proto.SerializeToString()
 
   with open(args.output_file, 'wb') as output: