HMACAuth broken in python 3

[bs610]

Python 3's change of string behaviour has affected the HMACAuth class. Two changes are required in auth.py:

1. Return a string from get_signature() instead of bytes. Without this, the call to format() results in a string like SRS:key:b'sig' instead of SRS:key:sig, and eventually you get a 401 Unauthorized:

@@ -35,7 +35,7 @@ class HMACAuth(AuthBase):
     def get_signature(self, r):
         canonical_string = self.get_canonical_string(r.url, r.headers, r.method)
         h = hmac.new(self.secret_key, canonical_string, digestmod=hashlib.sha1)
-        return base64.encodestring(h.digest()).strip()
+        return base64.encodestring(h.digest()).strip().decode('utf-8')

     def get_canonical_string(self, url, headers, method):
         parsedurl = urlparse(url)

2. Encode the output of get_canonical_string(). Without this, hmac.new() complains that unicode objects need to be encoded before hashing:

@@ -54,7 +54,7 @@ class HMACAuth(AuthBase):
         content_type = d_headers['content-type'] if 'content-type' in d_headers else ""
         date = d_headers['date']
         hash_buf = "%s\n%s\n%s\n%s\n%s\n" % (method, rpath, content_md5, content_type, date)
-        return hash_buf
+        return hash_buf.encode('utf-8')


 """

I have tested that these changes fix my auth problems in Python 3.6, and do not affect the behaviour in Python 2.7.