Fix response type classes hierarchy

gargantext/datasource/responses.py

@@ -38,16 +38,16 @@ class StreamableMixin(object):
         return super()._get_body()
 
 
-class TextResponse(StreamableMixin, BaseText):
+class TextResponse(StreamableMixin, BaseText, ABC):
     pass
 
 
-class HtmlResponse(StreamableMixin, BaseHtml, ABC): pass
-HtmlResponse.register(TextResponse)
+class HtmlResponse(StreamableMixin, BaseHtml): pass
+TextResponse.register(HtmlResponse)
 
 
-class XmlResponse(StreamableMixin, BaseXml, ABC): pass
-XmlResponse.register(TextResponse)
+class XmlResponse(StreamableMixin, BaseXml): pass
+TextResponse.register(XmlResponse)
 
 
 class ParseableResponse(TextResponse):