for #788 - the __nonzero__ method becomes __bool__ after 2to3, but it needs to return a bool (not int) type
for #788 - the __nonzero__ method becomes __bool__ after 2to3, but it needs to return a bool (not int) type

git-svn-id: 6d9763a5a770351123389058c013888add577529@13815 fe389314-cf27-0410-b35b-8c050e845b92

spacetelescope/stsci.tools