Looks like you're missing a jar. did you see any lines earlier in the build attempting to download dependencies?
The XWiki jars aren't hosted on central, but you can add the XWiki repository to your pom using configuration like this:
<repositories>
<repository>
<id>xwiki-releases</id>
<name>XWiki Maven2 Remote Repository for Releases</name>
<url>http://maven.xwiki.org/releases</url>
<releases>
<enabled>true</enabled>
</releases>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
</repositories>
Once that configuration is added, Maven should download all the required dependencies. If it still doesn't, you can explicitly add the missing dependency to your POM:
<dependencies>
...
<dependency>
<groupId>org.xwiki.platform</groupId>
<artifactId>xwiki-core-shared-tests</artifactId>
<version>??</version>
<scope>test<!--assume this is just for tests, if not omit the scope declaration--></scope>
</dependency>
</dependencies>