java.lang.NoClassDefFoundError: org/apache/http/conn/SchemePortResolver with AmazonHttpClient

I had a similar issue with my grails application. In my case the ClassNotFoundException was being thrown from a deploy script. For me the reason SchemePortResolver wasn't being resolved implicitly was because it wasn't required at compile time, it was needed at runtime. Here's what I added to my BuildConfig.groovy to fix it:

runtime 'org.apache.httpcomponents:httpclient:4.5.2' //Required by BeanstalkDeploy.groovy at runtime

Since the OP's question was for Maven, here's the equivalent include:

 <dependency>
   <groupId>org.apache.httpcomponents</groupId>
   <artifactId>httpclient</artifactId>
   <version>4.5.2</version>
   <scope>runtime</scope>
 </dependency>