class ViewModel::DeserializationError::DatabaseConstraint

def self.from_exception(exception, nodes = [])

back when we can't.
do our best to parse out what metadata we can from the error, and fall
Database constraint errors are pretty opaque and stringly typed. We can 
def self.from_exception(exception, nodes = [])
  case exception.cause
  when PG::UniqueViolation, PG::ExclusionViolation
    UniqueViolation.from_postgres_error(exception.cause, nodes)
  else
    self.new(exception.message, nodes)
  end
end

def initialize(detail, nodes = []) 

def initialize(detail, nodes = [])
  @detail = detail
  super(nodes)
end