Upgrade contextlib2 to 0.5.3
Upgrade contextlib2 to 0.5.3

karan/warehouse,alex/warehouse,wlonk/warehouse,karan/warehouse,wlonk/warehouse,alex/warehouse,alex/warehouse,dstufft/warehouse,alex/warehouse,karan/warehouse,pypa/warehouse,dstufft/warehouse,karan/warehouse,alex/warehouse,pypa/warehouse,pypa/warehouse,dstufft/warehouse,wlonk/warehouse,karan/warehouse,pypa/warehouse,dstufft/warehouse