* query.py: the message attribute of Exception was removed in Python 3,
replace e.message with e to format the new error message
* Fix test_complex_query_scenarios: convert
sample_item["metadata"]["util"] to float; "0.5" >= 0.5 is True in
Python 2, but it raises a TypeError on Python 3.
* tox.ini: add the following API v2 tests to Python 3.4:
- test_complex_query_scenarios.TestQueryMetersController.test_query_with_volume_field_name_orderby
Change-Id: I112e5564a65db005cf66ce967a8ac3e52fa95267