invalidation: don't create CacheInvalidation records on startup Creating the records early gave an advantage before lightweight was introduced. With lightweight it is no longer necessary. The records will be created on demand anyway and there is no reason to create and maintain them before they are used.

"""
Various utilities to work with Python < 2.7.

Those utilities may be deleted once ``vcs`` stops support for older Python
versions.
"""
import sys


if sys.version_info >= (2, 7):
    unittest = __import__('unittest')
else:
    unittest = __import__('unittest2')