diff -r bc6f5a1d8b7b -r 6e4334be0aaa mercurial/patch.py
--- a/mercurial/patch.py	Sat Apr 07 04:27:55 2007 -0300
+++ b/mercurial/patch.py	Sat Apr 07 04:27:55 2007 -0300
@@ -663,6 +663,8 @@
         single(repo.lookup(rev), seqno+1, fp)
 
 def diffstat(patchlines):
+    if not util.find_in_path('diffstat', os.environ.get('PATH', '')):
+        return
     fd, name = tempfile.mkstemp(prefix="hg-patchbomb-", suffix=".txt")
     try:
         p = popen2.Popen3('diffstat -p1 -w79 2>/dev/null > ' + name)