don't crash whole migrations if we cannot drop constraints. Those aren't so important. It might happen than older versions of rhodecode don't have those.
"""Various utilities to work with Python < 2.7.Those utilities may be deleted once ``vcs`` stops support for older Pythonversions."""importsysifsys.version_info>=(2,7):unittest=__import__('unittest')else:unittest=__import__('unittest2')