Revert removal of tokio_executor that causes tokio version mismatch panic

Cargo.lock

@@ -3800,6 +3800,7 @@ dependencies = [
  "sp-transaction-pool-api 2.0.0 (git+https://github.com/paritytech/substrate?branch=polkadot-master)",
  "sp-trie 2.0.0 (git+https://github.com/paritytech/substrate?branch=polkadot-master)",
  "tokio 0.2.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio-executor 0.2.0-alpha.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -6072,6 +6073,8 @@ version = "0.2.0-alpha.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "futures-util-preview 0.3.0-alpha.19 (registry+https://github.com/rust-lang/crates.io-index)",
+ "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio-sync 0.2.0-alpha.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]

validation/Cargo.toml

@@ -12,6 +12,7 @@ tokio = { version = "0.2.4", features = ["rt-core", "blocking"] }
 derive_more = "0.14.1"
 log = "0.4.8"
 exit-future = "0.2.0"
+tokio-executor = { version = "0.2.0-alpha.6", features = ["blocking"] }
 codec = { package = "parity-scale-codec", version = "1.1.0", default-features = false, features = ["derive"] }
 availability_store = { package = "polkadot-availability-store", path = "../availability-store" }
 parachain = { package = "polkadot-parachain", path = "../parachain" }

validation/src/lib.rs

@@ -747,7 +747,7 @@ enum CreateProposalState<C: Send + Sync, TxPool> {
 	/// Represents the state when we switch from pending to fired.
 	Switching,
 	/// Block proposing has fired.
-	Fired(tokio::task::JoinHandle<Result<Block, Error>>),
+	Fired(tokio_executor::blocking::Blocking<Result<Block, Error>>),
 }
 
 /// Inner data of the create proposal.
@@ -893,22 +893,18 @@ impl<C, TxPool> Future for CreateProposal<C, TxPool> where
 					thus Switching will never be reachable here; qed"
 				),
 			CreateProposalState::Fired(mut future) => {
-				let ret = Pin::new(&mut future)
-					.poll(cx)
-					.map(|res| res.map_err(Error::Join).and_then(|res| res));
+				let ret = Pin::new(&mut future).poll(cx);
 				self.state = CreateProposalState::Fired(future);
 				return ret
 			},
 		};
 
 		// 2. propose
-		let mut future = tokio::task::spawn_blocking(move || {
+		let mut future = tokio_executor::blocking::run(move || {
 			let proposed_candidates = data.table.proposed_set();
 			data.propose_with(proposed_candidates)
 		});
-		let polled = Pin::new(&mut future)
-			.poll(cx)
-			.map(|res| res.map_err(Error::Join).and_then(|res| res));
+		let polled = Pin::new(&mut future).poll(cx);
 		self.state = CreateProposalState::Fired(future);
 
 		polled