dg_mosaic.py: Make it work for python 2.4, 2.6, 2.7
dg_mosaic.py: Make it work for python 2.4, 2.6, 2.7

NeoGeographyToolkit/StereoPipeline,NeoGeographyToolkit/StereoPipeline,NeoGeographyToolkit/StereoPipeline,ScottMcMichael/StereoPipeline,DougFirErickson/StereoPipeline,aaronknister/StereoPipeline,NeoGeographyToolkit/StereoPipeline,njwilson23/StereoPipeline,oleg-alexandrov/StereoPipeline,njwilson23/StereoPipeline,njwilson23/StereoPipeline,njwilson23/StereoPipeline,oleg-alexandrov/StereoPipeline,NeoGeographyToolkit/StereoPipeline,njwilson23/StereoPipeline,DougFirErickson/StereoPipeline,ScottMcMichael/StereoPipeline,DougFirErickson/StereoPipeline,aaronknister/StereoPipeline,oleg-alexandrov/StereoPipeline,ScottMcMichael/StereoPipeline,ScottMcMichael/StereoPipeline,DougFirErickson/StereoPipeline,DougFirErickson/StereoPipeline,oleg-alexandrov/StereoPipeline,DougFirErickson/StereoPipeline,aaronknister/StereoPipeline,aaronknister/StereoPipeline,ScottMcMichael/StereoPipeline,njwilson23/StereoPipeline,oleg-alexandrov/StereoPipeline,oleg-alexandrov/StereoPipeline,ScottMcMichael/StereoPipeline,aaronknister/StereoPipeline,NeoGeographyToolkit/StereoPipeline