serde::export::From<std::io::Error> not implemented

[kevinw]

When building with nightly rust on Windows, I get the following error:

> rustc --version
rustc 1.22.0-nightly (4502e2aa9 2017-10-03)

> cargo build
error[E0277]: the trait bound `errors::Error: serde::export::From<std::io::Error>` is not satisfied
  --> world\src\mapfile.rs:39:5
   |
39 |     write!(output, "{}", MapSave { map, legend })?;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `serde::export::From<std::io::Error>` is not implemented for `errors::Error`
   |
   = help: the following implementations were found:
             <errors::Error as serde::export::From<ron::ser::Error>>
             <errors::Error as serde::export::From<ron::de::Error>>
             <errors::Error as serde::export::From<errors::ErrorKind>>
             <errors::Error as serde::export::From<&'a str>>
             <errors::Error as serde::export::From<std::string::String>>
   = note: required by `serde::export::From::from`

Is this an easy fix? I'm still learning error_chain and Rust in general.