Support latest rocket 0.4 (#940)

There was a regression:

https://github.com/SergioBenitez/Rocket/issues/1647

Fixes https://github.com/graphql-rust/juniper/issues/939.

juniper_rocket/CHANGELOG.md

@@ -1,5 +1,6 @@
 # master
 
+- Minimum `rocket` version is now `0.4.9`. Note this also bumps the [minimum required `rustc` version](https://github.com/SergioBenitez/Rocket/blob/v0.4/CHANGELOG.md#version-048-may-18-2021).
 - Compatibility with the latest `juniper`.
 
 # [[0.6.3] 2021-04-03](https://github.com/graphql-rust/juniper/releases/tag/juniper_rocket-0.6.3)

juniper_rocket/Cargo.toml

@@ -13,7 +13,7 @@ repository = "https://github.com/graphql-rust/juniper"
 
 [dependencies]
 juniper = { version = "0.15.5", path = "../juniper", default-features = false}
-rocket = { version = "0.4.2", default-features = false }
+rocket = { version = "0.4.9", default-features = false }
 serde_json = "1.0.2"
 
 [dev-dependencies]

juniper_rocket/src/lib.rs

@@ -277,10 +277,10 @@ where
         let mut body = String::new();
         data.open()
             .read_to_string(&mut body)
-            .map_err(|e| Err((Status::InternalServerError, format!("{:?}", e))))?;
+            .map_err(|e| (Status::InternalServerError, format!("{:?}", e)))?;
 
         Success(GraphQLRequest(if is_json {
-            serde_json::from_str(&body).map_err(|e| Err((Status::BadRequest, format!("{}", e))))?
+            serde_json::from_str(&body).map_err(|e| (Status::BadRequest, format!("{}", e)))?
         } else {
             GraphQLBatchRequest::Single(http::GraphQLRequest::new(body, None, None))
         }))