AttributeError: 'unicode' object has no attribute 'output_relative_to' after import data via zopyx.plone.migration

I used a modified version of zopyx.plone.migration importer script to import data into a Plone 5 site. All of the items are shown in the navigation area as well as where they suppose to be. However, whenever, I view an item, e.g. a Document content type, I'm shown this error:

Module ZPublisher.Publish, line 138, in publish
Module ZPublisher.mapply, line 77, in mapply
Module ZPublisher.Publish, line 48, in call_object
Module Products.Five.browser.metaconfigure, line 485, in __call__
Module Products.Five.browser.pagetemplatefile, line 125, in __call__
Module Products.Five.browser.pagetemplatefile, line 59, in __call__
Module zope.pagetemplate.pagetemplate, line 132, in pt_render
Module, line 98, in __call__
Module, line 163, in render
Module chameleon.zpt.template, line 261, in render
Module chameleon.template, line 191, in render
Module chameleon.template, line 171, in render
Module, line 246, in render
Module, line 1223, in render_master
Module, line 420, in render_content
Module, line 234, in __fill_content_core
Module, line 137, in render_content_core

AttributeError: 'unicode' object has no attribute 'output_relative_to'

   - Expression: "python:context.text.output_relative_to(view.context)"
   - Filename:   ... egg/plone/app/contenttypes/browser/templates/
   - Location:   (line 15: col 29)
   - Source:     ... ucture python:context.text.output_relative_to(view.context)"

Possibly is your "text" Attribute not an instance of RichTextValue . Look in the Docs to set the RichtTextValue correctly.
For Example:

from import RichTextValue

context.text = RichTextValue(u"Some input text", 'text/plain', 'text/html')