add blank lines in RST to separates blocks.

otherwise it is miss parsed.

fixes  #7907

IPython/nbconvert/templates/rst.tpl

@@ -12,7 +12,7 b''
 .. code:: python
 
 {{ cell.source | indent}}
-{%- endif -%}
+{% endif -%}
 {% endblock input %}
 
 {% block error %}
@@ -71,6 +71,12 b''
 {{ cell.source | markdown2rst }}
 {% endblock markdowncell %}
 
+{%- block rawcell scoped -%}
+{%- if cell.metadata.get('raw_mimetype', '').lower() in resources.get('raw_mimetypes', ['']) %}
+{{cell.source}}
+{% endif -%}
+{%- endblock rawcell -%}
+
 {% block headingcell scoped %}
 {{ ("#" * cell.level + cell.source) | replace('\n', ' ') | markdown2rst }}
 {% endblock headingcell %}