Tweak intrinsic error handling.
Tweak intrinsic error handling.

Better error messages, US spelling, more real checks.

graydon/rust,dwillmer/rust,aidancully/rust,GBGamer/rust,dwillmer/rust,dwillmer/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,GBGamer/rust,aidancully/rust,graydon/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust,dwillmer/rust,graydon/rust,dwillmer/rust,dwillmer/rust,GBGamer/rust,dwillmer/rust,GBGamer/rust,GBGamer/rust,dwillmer/rust,graydon/rust