vtkAVIWriter: make a more informative error message

Change-Id: I004963eee658bc75273350e381bba43be4b7fd7b
OpenGL: use STATUS for the OSMesa message

Change-Id: I3bced824fab1c6cfd10ac81f9484df161a9bd397
Merge topic 'better-encode-err-msg' into master

997f2ae1 vtkAVIWriter: make a more informative error message
Merge topic 'osmesa-message-output' into master

ea34fd86 OpenGL: use STATUS for the OSMesa message