2.x: fix warnings

Author: akarnokd

src/main/java/io/reactivex/internal/operators/flowable/FlowableOnBackpressureError.java

@@ -38,6 +38,7 @@ protected void subscribeActual(Subscriber<? super T> s) {
 
     static final class BackpressureErrorSubscriber<T>
             extends AtomicLong implements Subscriber<T>, Subscription {
+        private static final long serialVersionUID = -3176480756392482682L;
 
         final Subscriber<? super T> actual;
         Subscription s;

src/test/java/io/reactivex/TransformerTest.java

@@ -15,8 +15,6 @@
 
 import static org.junit.Assert.*;
 
-import java.io.IOException;
-
 import org.junit.Test;
 import org.reactivestreams.Publisher;
 

src/test/java/io/reactivex/internal/operators/flowable/FlowableFromSourceTest.java

@@ -13,8 +13,6 @@
 
 package io.reactivex.internal.operators.flowable;
 
-import static org.junit.Assert.*;
-
 import org.junit.*;
 import org.reactivestreams.*;
 

src/test/java/io/reactivex/internal/operators/observable/ObservableToXTest.java

@@ -52,7 +52,7 @@ public void toFlowableLatest() {
 
     @Test
     public void toFlowableError1() {
-        TestSubscriber<Integer> ts = Observable.range(1, 5)
+        Observable.range(1, 5)
         .toFlowable(BackpressureStrategy.ERROR)
         .test(1)
         .assertFailure(MissingBackpressureException.class, 1);