Why should std::env::var panic?

[cehteh]

I discovered a similar issue with std::process::Command env handling:

Lack of API mutating args at std::process::Command

Just some observation: arg_set() should return a Result<Command, Error> Which surprises me now since the env() functions don't return a Result but a Command. But there are certain ways which would fail setting an environment variable (illegal characters in its name). Is this intentional or a defect.

This might be fixed along with this in a similar way (that would be least surprising for the user)