Penman encoding errors are not caught by PyDelphin

[goodmami]

When doing a delphin convert operation, PyDelphin errors (if any) are caught and logged and then conversion proceeds. If there's a PenmanError when converting to/from dmrs-penman or eds-penman, the error is not caught and conversion stops.

A solution is to catch these errors where they occur and wrap them in a PyDelphinException so they are catchable by other parts of the code.