prevent IO operations on closed file
prevent IO operations on closed file

cache empty tile image as bytes and not StringIO, since some WSGI servers
(gunicorn) will close the StringIO file

vrsource/mapproxy,olt/mapproxy,camptocamp/mapproxy,geoadmin/mapproxy,kaiCu/mapproxy,mapproxy/mapproxy,procrastinatio/mapproxy,Anderson0026/mapproxy,kaiCu/mapproxy,geoadmin/mapproxy,mapproxy/mapproxy,vrsource/mapproxy,drnextgis/mapproxy,faegi/mapproxy,olt/mapproxy,camptocamp/mapproxy,procrastinatio/mapproxy,drnextgis/mapproxy,Anderson0026/mapproxy,faegi/mapproxy