Import exception types from Errors.py.
Import exception types from Errors.py.

Changed name from *Exception to *Error to be more consistent with
other Python packages.


git-svn-id: 8c9cf565d959f48f2495bfea3c697473c881f37a@199 67c13c2a-ce2d-4362-9fbd-a73952e22801

tschaume/gnuplot-py,tschaume/gnuplot-py