Pin freezegun on Python 3.3
freezegun version 0.3.11 has the common issue of incorrect PyPI metadata
mismatched with Requires-Python:
https://github.com/spulec/freezegun/issues/268
diff --git a/requirements-dev.txt b/requirements-dev.txt
index d6a6b53..c29f645 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -2,7 +2,8 @@
pytest >= 3.0; python_version != '3.3'
pytest < 3.3; python_version == '3.3'
pytest-cov >= 2.0.0
-freezegun
+freezegun < 0.3.11; python_version == '3.3'
+freezegun ; python_version != '3.3'
hypothesis >= 3.30
coverage
mock ; python_version < '3.0'