sha module is deprecated

This patch removes the deprecated warnings from the python
scripts.

Change-Id: I052a0aab3fb28dd1d78de1307edafda6b6c35e5f
diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index 52e7aed..fd098ea 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -20,7 +20,6 @@
 import os
 import platform
 import re
-import sha
 import shutil
 import subprocess
 import sys
@@ -29,6 +28,11 @@
 import time
 import zipfile
 
+try:
+  from hashlib import sha1 as sha1
+except ImportError:
+  from sha import sha as sha1
+
 # missing in Python 2.4 and before
 if not hasattr(os, "SEEK_SET"):
   os.SEEK_SET = 0
@@ -659,7 +663,7 @@
     self.name = name
     self.data = data
     self.size = len(data)
-    self.sha1 = sha.sha(data).hexdigest()
+    self.sha1 = sha1(data).hexdigest()
 
   def WriteToTemp(self):
     t = tempfile.NamedTemporaryFile()