Update your pom.xml file with the following:
<repository> <snapshots> <enabled>true</enabled> </snapshots> <id>boundless</id> <name>Boundless Maven Repository</name> <url>http://repo.boundlessgeo.com/main</url> </repository>
Using a repository manager allows us to better support "snapshot checksums".
This repository was used for the recent 12-RC1 release, if you find any other jars you would like deployed please give us a shout on the geotools-devel list.
Thanks to Justin, and Boundless, for continued build and release support.