Vendor dependencies

Let's see how I like this workflow.

vendor/tokio/tests/process_issue_42.rs

@@ -0,0 +1,38 @@
+#![warn(rust_2018_idioms)]
+#![cfg(feature = "full")]
+#![cfg(unix)]
+
+use futures::future::join_all;
+use std::process::Stdio;
+use tokio::process::Command;
+use tokio::task;
+
+#[tokio::test]
+async fn issue_42() {
+    // We spawn a many batches of processes which should exit at roughly the
+    // same time (modulo OS scheduling delays), to make sure that consuming
+    // a readiness event for one process doesn't inadvertently starve another.
+    // We then do this many times (in parallel) in an effort to stress test the
+    // implementation to ensure there are no race conditions.
+    // See alexcrichton/tokio-process#42 for background
+    let join_handles = (0..10usize).map(|_| {
+        task::spawn(async {
+            let processes = (0..10usize).map(|i| {
+                let mut child = Command::new("echo")
+                    .arg(format!("I am spawned process #{}", i))
+                    .stdin(Stdio::null())
+                    .stdout(Stdio::null())
+                    .stderr(Stdio::null())
+                    .kill_on_drop(true)
+                    .spawn()
+                    .unwrap();
+
+                async move { child.wait().await }
+            });
+
+            join_all(processes).await;
+        })
+    });
+
+    join_all(join_handles).await;
+}