Migrate from failure to anyhow

This moves from a custom error trait to the standard `Error` trait,
improving ecosystem interoperability.

Cargo.toml

@@ -20,7 +20,7 @@ exclude = [
 [dependencies]
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
-failure = "0.1.2"
+anyhow = "1.0.0"
 log = "0.4.1"
 
 [dev-dependencies]

src/lib.rs

@@ -2,8 +2,6 @@
 
 #[macro_use]
 extern crate log;
-#[macro_use]
-extern crate failure;
 #[cfg(test)]
 #[macro_use]
 extern crate proptest;
@@ -12,7 +10,7 @@ use serde_json;
 use std::collections::HashSet;
 use std::ops::Range;
 
-use failure::Error;
+use anyhow::Error;
 
 pub mod diagnostics;
 use crate::diagnostics::{Diagnostic, DiagnosticSpan};

src/replace.rs

@@ -2,7 +2,7 @@
 //! replacement of parts of its content, with the ability to prevent changing
 //! the same parts multiple times.
 
-use failure::Error;
+use anyhow::{Error, ensure, anyhow};
 use std::rc::Rc;
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -133,7 +133,7 @@ impl Data {
                         );
                     }
 
-                    format_err!(
+                    anyhow!(
                         "Could not replace range {}...{} in file \
                          -- maybe parts of it were already replaced?",
                         from,