fix: panicking when can't create runtime for block_on (#2905)

cli/tokio_util.rs

 // Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
 use crate::resources::Resource;
+use deno::ErrBox;
 use futures;
 use futures::Future;
 use futures::Poll;
@@ -10,11 +11,11 @@ use tokio;
 use tokio::net::TcpStream;
 use tokio::runtime;
 
-pub fn create_threadpool_runtime() -> tokio::runtime::Runtime {
+pub fn create_threadpool_runtime(
+) -> Result<tokio::runtime::Runtime, tokio::io::Error> {
   runtime::Builder::new()
     .panic_handler(|err| std::panic::resume_unwind(err))
     .build()
-    .unwrap()
 }
 
 pub fn run<F>(future: F)
@@ -22,7 +23,7 @@ where
   F: Future<Item = (), Error = ()> + Send + 'static,
 {
   // tokio::runtime::current_thread::run(future)
-  let rt = create_threadpool_runtime();
+  let rt = create_threadpool_runtime().expect("Unable to create Tokio runtime");
   rt.block_on_all(future).unwrap();
 }
 
@@ -39,22 +40,27 @@ where
 /// given future. This is useful when we want to block the main runtime to
 /// resolve a future without worrying that we'll use up all the threads in the
 /// main runtime.
-pub fn block_on<F, R, E>(future: F) -> Result<R, E>
+pub fn block_on<F, R>(future: F) -> Result<R, ErrBox>
 where
-  F: Send + 'static + Future<Item = R, Error = E>,
+  F: Send + 'static + Future<Item = R, Error = ErrBox>,
   R: Send + 'static,
-  E: Send + 'static,
 {
   use std::sync::mpsc::channel;
   use std::thread;
   let (sender, receiver) = channel();
   // Create a new runtime to evaluate the future asynchronously.
   thread::spawn(move || {
-    let mut rt = create_threadpool_runtime();
-    let r = rt.block_on(future);
-    sender.send(r).unwrap();
+    let r = match create_threadpool_runtime() {
+      Ok(mut rt) => rt.block_on(future),
+      Err(e) => Err(ErrBox::from(e)),
+    };
+    sender
+      .send(r)
+      .expect("Unable to send blocking future result")
   });
-  receiver.recv().unwrap()
+  receiver
+    .recv()
+    .expect("Unable to receive blocking future result")
 }
 
 // Set the default executor so we can use tokio::spawn(). It's difficult to
@@ -65,7 +71,7 @@ pub fn init<F>(f: F)
 where
   F: FnOnce(),
 {
-  let rt = create_threadpool_runtime();
+  let rt = create_threadpool_runtime().expect("Unable to create Tokio runtime");
   let mut executor = rt.executor();
   let mut enter = tokio_executor::enter().expect("Multiple executors at once");
   tokio_executor::with_default(&mut executor, &mut enter, move |_enter| f());