Adding hack alternative method for assertThrows() since it was never …

…released in JUnit4 (google uses a snapshot internally).

RELNOTES=n/a

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=197941045

google/src/test/java/com/google/common/flogger/GoogleLoggerTest.java

@@ -19,7 +19,7 @@
 import static com.google.common.flogger.LazyArgs.lazy;
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.common.truth.Truth.assertWithMessage;
-import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.fail;
 
 import com.google.common.base.Supplier;
 import com.google.common.flogger.backend.KeyValueHandler;
@@ -261,4 +261,14 @@ public void close() {
       logRecords = null;
     }
   }
+
+  // Hack version of the JUnit 4.13 assertThrows() method that's not available everywhere.
+  private static void assertThrows(Class<? extends RuntimeException> err, Runnable fn) {
+    try {
+      fn.run();
+      fail("expected exception of type " + err.getName());
+    } catch (RuntimeException e) {
+      assertThat(e).isInstanceOf(err);
+    }
+  }
 }