v0.5.5 - Better Error Messaging

New Feature

• Improved ValidationError messaging, including more details on property errors and info about underlying errors on Union and Instance property validation (See: #261)

Bug Fixes

• Remove functools.wraps on serializer/deserializer functions to fix Python 2 bug (See: https://github.com/gmggroup/omf/issues/30 and #265)