Take back setting algorithm to default twice

Author: fulder

httpsig/sign.py

@@ -108,6 +108,9 @@ class HeaderSigner(Signer):
        'authorization'.
     """
     def __init__(self, key_id, secret, algorithm=None, sign_algorithm=None, headers=None, sign_header='authorization'):
+        if algorithm is None:
+            algorithm = DEFAULT_SIGN_ALGORITHM
+
         super(HeaderSigner, self).__init__(secret=secret, algorithm=algorithm, sign_algorithm=sign_algorithm)
         self.headers = headers or ['date']
         self.signature_template = build_signature_template(