Update to Rust 2018

1 job for fix-borrow in 1 minute and 53 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
failed #16424
build

00:01:53

 
Name Stage Failure
failed
build Test
   |         ^^^^^^^ no `Context` external crate

error: aborting due to 5 previous errors

For more information about this error, try `rustc --explain E0432`.
error: Could not compile `liner`.
warning: build failed, waiting for other jobs to finish...
error: build failed
ERROR: Job failed: exit code 1