Only uses captureWarnings() if available
Only uses captureWarnings() if available

Although not mentioned in the doc, captureWarnings() was introduced in
2.7.

Nikea/VisTrails,minesense/VisTrails,hjanime/VisTrails,Nikea/VisTrails,minesense/VisTrails,VisTrails/VisTrails,hjanime/VisTrails,minesense/VisTrails,VisTrails/VisTrails,Nikea/VisTrails,VisTrails/VisTrails,hjanime/VisTrails,celiafish/VisTrails,Nikea/VisTrails,hjanime/VisTrails,celiafish/VisTrails,VisTrails/VisTrails,minesense/VisTrails,celiafish/VisTrails,hjanime/VisTrails,celiafish/VisTrails,minesense/VisTrails,VisTrails/VisTrails