Switch care_map_generator.py to Python 3.

This is the last remaining use of the python-symbol library
from Python 2.

Test: Ran 2to3 on the script, no changes reported.
Change-Id: I9c8bf4840eaf1832cabc4b6af831f5c2de554d4f
diff --git a/update_verifier/Android.bp b/update_verifier/Android.bp
index f9a8341..ff2eff9 100644
--- a/update_verifier/Android.bp
+++ b/update_verifier/Android.bp
@@ -121,12 +121,12 @@
 
     version: {
         py2: {
-            enabled: true,
-            embedded_launcher: true,
-        },
-        py3: {
             enabled: false,
             embedded_launcher: false,
         },
+        py3: {
+            enabled: true,
+            embedded_launcher: true,
+        },
     },
 }
diff --git a/update_verifier/care_map_generator.py b/update_verifier/care_map_generator.py
index 051d98d..c6f2dad 100644
--- a/update_verifier/care_map_generator.py
+++ b/update_verifier/care_map_generator.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright (C) 2018 The Android Open Source Project
 #
@@ -115,13 +115,13 @@
     content = input_care_map.read()
 
   if args.parse_proto:
-    result = ParseProtoMessage(content, args.fingerprint_enabled)
+    result = ParseProtoMessage(content, args.fingerprint_enabled).encode()
   else:
     care_map_proto = GenerateCareMapProtoFromLegacyFormat(
         content.rstrip().splitlines(), args.fingerprint_enabled)
     result = care_map_proto.SerializeToString()
 
-  with open(args.output_file, 'w') as output:
+  with open(args.output_file, 'wb') as output:
     output.write(result)