silence callable warning in hmac
diff --git a/Lib/hmac.py b/Lib/hmac.py
index 729ef38..5388106 100644
--- a/Lib/hmac.py
+++ b/Lib/hmac.py
@@ -41,7 +41,7 @@
             import hashlib
             digestmod = hashlib.md5
 
-        if callable(digestmod):
+        if hasattr(digestmod, '__call__'):
             self.digest_cons = digestmod
         else:
             self.digest_cons = lambda d='': digestmod.new(d)