[util] turns contract assertion into IAE

... to make it independent of JVM flags

platform/util/src/com/intellij/util/concurrency/Semaphore.java

@@ -1,18 +1,4 @@
-/*
- * Copyright 2000-2016 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
+// Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 package com.intellij.util.concurrency;
 
 import com.intellij.openapi.progress.ProcessCanceledException;
@@ -30,7 +16,9 @@ public class Semaphore {
    * Creates a semaphore and immediately puts it down the specified number of times
    */
   public Semaphore(int downs) {
-    assert downs >= 0 : "A nonnegative amount of 'downs' expected, found " + downs;
+    if (downs < 0) {
+      throw new IllegalArgumentException("A non-negative amount of 'downs' expected, found " + downs);
+    }
     for (int i = 0; i < downs; i++) {
       down();
     }