fix UnavailablePreviewType test

tracim/tests/functional/test_contents.py

         )
         assert res.content_type == 'application/pdf'
 
-    @pytest.mark.xfail(reason='TODO')
-    def test_api__get_full_pdf_preview__err__400__jpg_UnavailablePreviewType(self) -> None:
+    def test_api__get_full_pdf_preview__err__400__png_UnavailablePreviewType(self) -> None:
         """
         Set one file of a content
         """
         )
         res = self.testapp.get(
             '/api/v2/workspaces/1/files/{}/preview/pdf/full'.format(content_id), # nopep8
-            status=200
+            status=400
         )
-        assert res.content_type == ''
 
 
 class TestThreads(FunctionalTest):

tracim/views/contents_api/file_controller.py

 import transaction
 from depot.io.local import LocalStoredFile
 from depot.manager import DepotManager
+from preview_generator.exception import UnavailablePreviewType
 from pyramid.config import Configurator
 from pyramid.response import FileResponse, FileIter
 
     @hapic.with_api_doc(tags=[FILE_ENDPOINTS_TAG])
     @require_workspace_role(UserRoleInWorkspace.READER)
     @require_content_types([file_type])
+    @hapic.handle_exception(UnavailablePreviewType, HTTPStatus.BAD_REQUEST)
     @hapic.input_query(PageQuerySchema())
     @hapic.input_path(WorkspaceAndContentIdPathSchema())
     @hapic.output_file([])
     @hapic.with_api_doc(tags=[FILE_ENDPOINTS_TAG])
     @require_workspace_role(UserRoleInWorkspace.READER)
     @require_content_types([file_type])
+    @hapic.handle_exception(UnavailablePreviewType, HTTPStatus.BAD_REQUEST)
     @hapic.input_path(WorkspaceAndContentIdPathSchema())
     @hapic.output_file([])
     def preview_pdf_full(self, context, request: TracimRequest, hapic_data=None):
     @hapic.with_api_doc(tags=[FILE_ENDPOINTS_TAG])
     @require_workspace_role(UserRoleInWorkspace.READER)
     @require_content_types([file_type])
+    @hapic.handle_exception(UnavailablePreviewType, HTTPStatus.BAD_REQUEST)
     @hapic.input_path(WorkspaceAndContentRevisionIdPathSchema())
     @hapic.input_query(PageQuerySchema())
     @hapic.output_file([])