If you use the Plain Java Client zip of jars for accessing the Jazz Team Server/repository you may need to use this workaround.

With the RTC 3.0 M8 build we've noticed that there is a key jar file missing. The issue has been reported and the development team has the fix in place for the next milestone. The workaround is to copy the jar file from the Rational Team Concert Eclipse Client install to the unzipped PJC folder.

This is the name of the jar you want to copy:
org.apache.commons.httpclient_3.1.0.v20080605-1935.jar

(At least this was the version we saw when using an early build of the M8 drop.)

The location of the jar will depend on how you installed the Rational Team Concert Eclipse Client:
If you used Installation Manager the jar will be found in the
<install>\IBMIMShared\plugins directory.
If you installed using a zip file the jar will be found in the
<install>\client\eclipse\plugins directory.

This is the bug report of interest:
https://jazz.net/jazz/web/projects/Rational%20Team%20Concert#action=com.ibm.team.workitem.viewWorkItem&id=127685