add a server with anypoint cloud platform credentials and a profile for archetype-repo in you .m2 > settings.xml file before publishing custom policy

MuleCustomPolicy_settings.xml

<servers>
    <server>
      <id>exchange-server</id>
      <username>anypoint_username</username>
      <password>anypoint_password</password>
    </server>  
</servers>


<profiles>  
  <profile>
	<id>archetype-repository</id>
	<repositories>
	  <repository>
	  <id>archetype</id>
	  <name>Mule Repository</name>
	  <url>https://repository-master.mulesoft.org/nexus/content/repositories/public</url>
	  <releases>
	    <enabled>true</enabled>
	    <checksumPolicy>fail</checksumPolicy>
	  </releases>
	  <snapshots>
	    <enabled>true</enabled>
	    <checksumPolicy>warn</checksumPolicy>
	  </snapshots>
	  </repository>
	</repositories>
   </profile> 
</profiles>