Errors when using package

No Rosinstall 0.5 Libraries

Example:

ERROR Cannot find rosinstall libraries, check your installation. One frequent cause is that rosinstall 0.5 is still installed in /usr/local/lib. Check the rosinstall wiki for solutions.
No module named pkg_resources

Solution:

Be sure to read the line following the complaint. The above hints that it is missing the python module 'pkg_resources' which is in setuptools. Usually it will be this, or another dependency that is missing.