trait objects without an explicit `dyn` are deprecated

[AndyGauge]

--> src/error_chain.rs:525:35
|
525 | fn extract_backtrace(e: &(::std::error::Error + Send + 'static))
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use dyn: dyn ::std::error::Error + Send + 'static
|
::: src/example_generated.rs:24:5
|
24 | error_chain!{}
| -------------- in this macro invocation
|
= note: -D bare-trait-objects implied by -D warnings
error: trait objects without an explicit dyn are deprecated