message: Fix compilation with serde 1.0.122
  This may or may not be a bug in serde, but let's commit a fix here first
  in any case.
  Closes
diff: @@ -527,7 +527,7 @@ impl<'de, 'config> de::MapAccess<'de> for ValueDeserializer<'config> {
  seed.deserialize(Tuple2Deserializer(0i32, path.to_string_lossy()))
  }
  Definition::Environment(env) => {
  - seed.deserialize(Tuple2Deserializer(1i32, env.as_ref()))
  + seed.deserialize(Tuple2Deserializer(1i32, env.as_str()))
  }
  Definition::Cli => seed.deserialize(Tuple2Deserializer(2i32, "")),
  }
  