challenge2.rs test failure

Test Output

guita@David-Asus MINGW64 /c/Development/Rust/projects/cryptowise (master)
$ cargo test
     Running target\debug\cryptowise-637d5e98fd8788fc.exe

running 2 tests
test set1::challenge1::tests::it_works ... ok
test set1::challenge2::tests::it_works2 ... ok

test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured

     Running target\debug\lib-4c8d0b756a010da9.exe

running 1 test
test it_works ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured

   Doc-tests cryptowise

running 4 tests
test set1::challenge2_0 ... FAILED
test set1::challenge2_0 ... FAILED
test set1::challenge1_0 ... ok
test set1::challenge1_0 ... ok

failures:

---- set1::challenge2_0 stdout ----
        <anon>:4:5: 4:32 error: unresolved import `rustc_serialize::hex::ToHex`. Maybe a missing `extern crate rustc_serialize`? [E0432]
<anon>:4 use rustc_serialize::hex::ToHex;
             ^~~~~~~~~~~~~~~~~~~~~~~~~~~
<anon>:8:58: 8:64 error: no method named `to_hex` found for type `std::vec::Vec<u8>` in the current scope
<anon>:8 assert_eq!("746865206b696420646f6e277420706c6179",result.to_hex());
                                                                  ^~~~~~
<anon>:8:1: 8:68 note: in this expansion of assert_eq! (defined in <std macros>)
<anon>:8:58: 8:64 help: items from traits can only be used if the trait is in scope; the following trait is implemented but not in scope, perhaps add a `use` for it:
<anon>:8:58: 8:64 help: candidate #1: `use rustc_serialize::hex::ToHex`
error: aborting due to previous error(s)
thread 'set1::challenge2_0' panicked at 'Box<Any>', ../src/librustc\session/mod.rs:170
note: Run with `RUST_BACKTRACE=1` for a backtrace.

---- set1::challenge2_0 stdout ----
        <anon>:4:5: 4:32 error: unresolved import `rustc_serialize::hex::ToHex`. Maybe a missing `extern crate rustc_serialize`? [E0432]
<anon>:4 use rustc_serialize::hex::ToHex;
             ^~~~~~~~~~~~~~~~~~~~~~~~~~~
<anon>:8:58: 8:64 error: no method named `to_hex` found for type `std::vec::Vec<u8>` in the current scope
<anon>:8 assert_eq!("746865206b696420646f6e277420706c6179",result.to_hex());
                                                                  ^~~~~~
<anon>:8:1: 8:68 note: in this expansion of assert_eq! (defined in <std macros>)
<anon>:8:58: 8:64 help: items from traits can only be used if the trait is in scope; the following trait is implemented but not in scope, perhaps add a `use` for it:
<anon>:8:58: 8:64 help: candidate #1: `use rustc_serialize::hex::ToHex`
error: aborting due to previous error(s)
thread 'set1::challenge2_0' panicked at 'Box<Any>', ../src/librustc\session/mod.rs:170


failures:
    set1::challenge2_0
    set1::challenge2_0

test result: FAILED. 2 passed; 2 failed; 0 ignored; 0 measured

error: test failed