using a py3 marker instead of a try..except

--HG--
branch : distribute
extra : rebase_source : e3ccffb120f1fdaddfa0746c0a592d6fbaf0dcd1

setuptools/command/upload_docs.py

@@ -12,11 +12,14 @@ import httplib
 import base64
 import urlparse
 import tempfile
+import sys
 
 from distutils import log
 from distutils.errors import DistutilsOptionError
 from distutils.command.upload import upload
 
+_IS_PYTHON3 = sys.version > '3'
+
 try:
     bytes
 except NameError:
@@ -89,10 +92,10 @@ class upload_docs(upload):
         }
         # set up the authentication
         credentials = self.username + ':' + self.password
-        try:  # base64 only works with bytes in Python 3.
+        if _IS_PYTHON3:  # base64 only works with bytes in Python 3.
             encoded_creds = base64.encodebytes(credentials.encode('utf8'))
             auth = bytes("Basic ")
-        except AttributeError:
+        else:
             encoded_creds = base64.encodestring(credentials)
             auth = "Basic "
         auth += encoded_creds.strip()