Update nitrokey dependency to 0.6.0

nitrokey 0.6.0 introduced the SerialNumber struct (instead of
representing serial numbers as strings). We no longer have to manually
format the serial number as SerialNumber implements Display.

Import subrepo nitrokey/:nitrokey at 2a8ce725407f32db5ad61c37475719737c9b5c9c

1 files changed, 1 insertions, 1 deletions

diff --git a/nitrokey/tests/pws.rs b/nitrokey/tests/pws.rs
index 7169695..47e9703 100644
--- a/nitrokey/tests/pws.rs
+++ b/nitrokey/tests/pws.rs
@@ -16,7 +16,7 @@ use nitrokey_test::test as test_device;
 fn get_slot_name_direct(slot: u8) -> Result<String, Error> {
     let ptr = unsafe { nitrokey_sys::NK_get_password_safe_slot_name(slot) };
     if ptr.is_null() {
-        return Err(Error::UnexpectedError);
+        return Err(Error::UnexpectedError("null pointer".to_owned()));
     }
     let s = unsafe { CStr::from_ptr(ptr).to_string_lossy().into_owned() };
     unsafe { free(ptr as *mut c_void) };