rand: bubble up IO messages futher.

The various ...Rng::new() methods can hit IO errors from the OSRng they use,
and it seems sensible to expose them at a higher level. Unfortunately, writing
e.g. `StdRng::new().unwrap()` gives a much poorer error message than if it
failed internally, but this is a problem with all `IoResult`s.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/libstd/io/fs.rs b/src/libstd/io/fs.rs
index e66aa8c0046..63973584c1e 100644
--- a/src/libstd/io/fs.rs
+++ b/src/libstd/io/fs.rs
@@ -1285,7 +1285,7 @@ mod test {
         use rand::{StdRng, Rng};
 
         let mut bytes = [0, ..1024];
-        StdRng::new().fill_bytes(bytes);
+        StdRng::new().unwrap().fill_bytes(bytes);
 
         let tmpdir = tmpdir();