catch BlockingIOError exception on unsuccessful attempt to get lock, fix python3.3 compatibility (#434)
catch BlockingIOError exception on unsuccessful attempt to get lock, fix python3.3 compatibility (#434)


camptocamp/mapproxy,drnextgis/mapproxy,mapproxy/mapproxy,drnextgis/mapproxy,camptocamp/mapproxy,mapproxy/mapproxy