Stop logging all registry client exceptions

Not all exceptions need to be logged as ERROR in the glance-api
log when - for instance, a user asking for an image that does not
exist doesn't mean an ERROR actually occurred. This logs the exception
name at INFO level. An ERROR won't be logged at all, even in
the case of a 500-level response from glance-registry. An operator
would be alerted with an ERROR log in the glance-registry log in that
case.

Fixes bug 1079211.

Change-Id: Ie2bba3105f8d9f3de97bc50132fb046baf710a90

glance/registry/client.py

@@ -94,9 +94,10 @@ class RegistryClient(BaseClient):
                     " request id %(request_id)s")
             LOG.debug(msg % locals())
 
-        except:
-            LOG.exception(_("Registry request %(method)s %(action)s "
-                            "Exception") % locals())
+        except Exception as exc:
+            exc_name = exc.__class__.__name__
+            LOG.info(_("Registry client request %(method)s %(action)s "
+                       "raised %(exc_name)s") % locals())
             raise
         return res