Expose to user mongoengine.base.NON_FIELD_ERRORS

This variable is used to set the field containing the errors raised in a
clean function. Given those function are user-defined, users should be
able to get the name of the field to easily retreive their custom errors.

Author: touilleMan

mongoengine/base/document.py

@@ -19,7 +19,7 @@
 from mongoengine.errors import (FieldDoesNotExist, InvalidDocumentError,
                                 LookUpError, OperationError, ValidationError)
 
-__all__ = ('BaseDocument',)
+__all__ = ('BaseDocument', 'NON_FIELD_ERRORS')
 
 NON_FIELD_ERRORS = '__all__'