Introduce constants 
Introduce constants 

to reduce error surface and improve test consistency.
DualSpark/rust-aws,SecurityInsanity/rusoto,DualSpark/rust-aws,DualSpark/rusoto,mattico/rusoto,rusoto/rusoto,rusoto/rusoto,rusoto/rusoto,mattico/rusoto,DualSpark/rusoto,DualSpark/rusoto,SecurityInsanity/rusoto,mattico/rusoto,DualSpark/rust-aws