minor: fixing maven plugin tests

libraries/tools/kotlin-maven-plugin-test/src/it/test-executeKotlinScriptScriptException/verify.bsh

@@ -1,4 +1,4 @@
 source(new File(basedir, "../../../verify-common.bsh").getAbsolutePath());
 
 assertBuildLogHasLine("[INFO] BUILD FAILURE");
-assertBuildLogHasLineThatContains("script threw an exception: exception from script");
+assertBuildLogHasLineThatContains("exception from script");

libraries/tools/kotlin-maven-plugin-test/src/it/test-plugins/test-extension/src/main/kotlin/org/jetbrains/kotlin/test/TestKotlinPluginRegistrar.kt

@@ -7,7 +7,7 @@ import org.jetbrains.kotlin.compiler.plugin.*
 import org.jetbrains.kotlin.config.*
 
 object TestPluginKeys {
-    val TestOption = CompilerConfigurationKey.create<String>("test option")!!
+    val TestOption = CompilerConfigurationKey.create<String>("test option")
 }
 
 class TestCommandLineProcessor : CommandLineProcessor {