Change exception class from monascaclient

monascaclient was recently migrated to
use 'osc' library. Due to that, exception
classes has been changed. This commit adjusts
the exception class to recently released
monascaclient==1.7.0

Depends-On: Ie647221a3ab055e7b150d65ffb9287b44ef834cb
Change-Id: Icfef345c4269ac4cb682049f22a43fdab3d39845

watcher/datasource/monasca.py

@@ -33,7 +33,7 @@ class MonascaHelper(object):
     def query_retry(self, f, *args, **kwargs):
         try:
             return f(*args, **kwargs)
-        except exc.HTTPUnauthorized:
+        except exc.Unauthorized:
             self.osc.reset_clients()
             self.monasca = self.osc.monasca()
             return f(*args, **kwargs)