formencode htmlfill in jinja2 template

gistfile1.py

# htmlfill
with app.test_request_context('/'):
    html = render_template_string('''
        {%- autoescape true -%}
          {%- form 'user.signin', {'method': 'POST'}
              with {'name': 'sohee', 'pretty': 'no'},
                   {'pretty': 'sohee is always pretty.'} -%}
            <input type="text" name="name" /> {{- '' -}}
            <input type="text" name="pretty" placeholder="yes" /> {{- '' -}}
            <div id="errors"> {{- '' -}}
              <form:error name="name"> {{- '' -}}
              <form:error name="pretty"> {{- '' -}}
            </div>
          {%- endform -%}
        {%- endautoescape -%}
    ''')
expected = ('<form action="/u/signin" method="POST">'
            '<input type="text" name="name" value="sohee" />'
            '<input type="text" name="pretty" placeholder="yes"'
            ' class="error" value="no" />'
            '<div id="errors">'
            '<p class="error">sohee is always pretty.</p>'
            '</div>'
            '</form>')
assert html == expected