Remove usage of deprecated and dropped Exception.message attribute

Change-Id: I9e3f76d1c43e700ae2e766012b5deadb33c3a6f1

freezer_ui/api/api.py

@@ -311,7 +311,7 @@ class Session(object):
                                               v['result'])
                     for k, v in session['jobs'].iteritems()]
         except AttributeError as error:
-            LOG.error(error.message)
+            LOG.exception(error)
         return jobs
 
     def _build(self, session):

freezer_ui/utils.py

@@ -200,7 +200,7 @@ def shield(message, redirect=''):
             try:
                 return function(view, *args, **kwargs)
             except Exception as error:
-                LOG.error(error.message)
+                LOG.exception(error)
                 namespace = "horizon:disaster_recovery:"
                 r = reverse("{0}{1}".format(namespace, redirect))
 
@@ -208,10 +208,10 @@ def shield(message, redirect=''):
                     # To avoid an endless loop, we must not redirect to the
                     # same page on which the error happened
                     user_home = get_user_home(view.request.user)
-                    exceptions.handle(view.request, _(error.message),
+                    exceptions.handle(view.request, _(str(error)),
                                       redirect=user_home)
                 else:
-                    exceptions.handle(view.request, _(error.message),
+                    exceptions.handle(view.request, _(str(error)),
                                       redirect=r)
 
         return wrapped_function