[This line](https://github.com/rust-lang-nursery/rustup.rs/blob/cd0d20166fab04be043c92c8c0136bf52f3224ee/src/rustup/toolchain.rs#L75) checks whether a toolchain exists by looking up the directory, but custom toolchains use symlinks so this check fails.
This line checks whether a toolchain exists by looking up the directory, but custom toolchains use symlinks so this check fails.