Fix build error

pom.xml

@@ -885,8 +885,7 @@
       <dependency>
         <groupId>org.clapper</groupId>
         <artifactId>classutil_${scala.binary.version}</artifactId>
-        <version>1.5.0</version>
-        <scope>test</scope>
+        <version>1.5.1</version>
       </dependency>
       <dependency>
         <groupId>org.scalatest</groupId>

sql/catalyst/pom.xml

@@ -120,6 +120,7 @@
     <dependency>
       <groupId>org.clapper</groupId>
       <artifactId>classutil_${scala.binary.version}</artifactId>
+      <scope>test</scope>
     </dependency>
   </dependencies>
   <build>

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/datetimeExpressions.scala

@@ -871,7 +871,7 @@ case class UnixTimestamp(timeExp: Expression, format: Expression, timeZoneId: Op
 }
 
 abstract class ToTimestamp
-  extends BinaryExpression with TimeZoneAwareExpression with ExpectsInputTypes with NullIntolerant {
+  extends BinaryExpression with TimeZoneAwareExpression with ExpectsInputTypes {
 
   // The result of the conversion to timestamp is microseconds divided by this factor.
   // For example if the factor is 1000000, the result of the expression is in seconds.

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/NullIntolerantCheckerSuite.scala

@@ -31,7 +31,6 @@ class NullIntolerantCheckerSuite extends SparkFunSuite {
   // Do not check these Expressions
   private val whiteList = List(
     classOf[IntegralDivide], classOf[Divide], classOf[Remainder], classOf[Pmod],
-    classOf[ToUnixTimestamp], classOf[GetTimestamp], classOf[UnixTimestamp],
     classOf[CheckOverflow], classOf[NormalizeNaNAndZero],
     classOf[InSet],
     classOf[PrintToStderr], classOf[CodegenFallbackExpression]).map(_.getName)

tools/pom.xml

@@ -44,7 +44,6 @@
     <dependency>
       <groupId>org.clapper</groupId>
       <artifactId>classutil_${scala.binary.version}</artifactId>
-      <version>1.5.1</version>
     </dependency>
   </dependencies>