use 'hg identify' to generate .hgrev file

setup.py

@@ -6,10 +6,9 @@ import sys
 if 'sdist' in sys.argv and sys.platform != "win32" and sys.version_info >= (2,4):
     # Record the current revision in .hgrev
     import subprocess # os.popen is cleaner but deprecated
-    changset = subprocess.Popen("hg log --rev tip | grep changeset", 
-                                shell=True,
-                                stdout=subprocess.PIPE).stdout.read()
-    rev = changset.decode('ISO-8859-1').split(':')[-1].strip()
+    changeset = subprocess.Popen("hg identify --id --rev tip".split(),
+                                 stdout=subprocess.PIPE).stdout.read()
+    rev = changeset.decode('ISO-8859-1').strip()
     hgrev = open('.hgrev', 'w')
     hgrev.write(rev)
     hgrev.close()