Make common.py python3 compatible

Test: th
Change-Id: Ibe4db0a367b7b8df5eeb7f2a6d0816e8e18bf342
diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index 26c4ae8..acd978f 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -663,7 +663,7 @@
   """Extracts the contents of fn from input zipfile or directory into a file."""
   if isinstance(input_file, zipfile.ZipFile):
     tmp_file = MakeTempFile(os.path.basename(fn))
-    with open(tmp_file, 'w') as f:
+    with open(tmp_file, 'wb') as f:
       f.write(input_file.read(fn))
     return tmp_file
   else:
@@ -887,8 +887,8 @@
     prop_file = GetBootImageBuildProp(boot_img)
     if prop_file is None:
       return ''
-    with open(prop_file) as f:
-      return f.read().decode()
+    with open(prop_file, "r") as f:
+      return f.read()
 
   @staticmethod
   def _ReadPartitionPropFile(input_file, name):