message: Fix test failure on nightly due to `codemap::Span` change.
  Update due to rust-lang/rust#52953.
diff: @@ -220,7 +220,7 @@ fn plugin_deps() {
  use rustc_plugin::Registry;
  use syntax::tokenstream::TokenTree;
  - use syntax::codemap::Span;
  + use syntax::source_map::Span;
  use syntax::ast::*;
  use syntax::ext::base::{ExtCtxt, MacEager, MacResult};
  use syntax::ext::build::AstBuilder;
  @@ -320,7 +320,7 @@ fn plugin_to_the_max() {
  use rustc_plugin::Registry;
  use syntax::tokenstream::TokenTree;
  - use syntax::codemap::Span;
  + use syntax::source_map::Span;
  use syntax::ast::*;
  use syntax::ext::base::{ExtCtxt, MacEager, MacResult};
  use syntax::ext::build::AstBuilder;
  