I can remove that if you prefer so. It's done in this way because I
wanted to include the urls for the specification in the ErrorMessage and
they are quite long. There are other ways to implement that and since I
don't see why the one implementation is better than the other I just
chose to use different Error classes.

|if m.end() != len(name)| is excluded by both the plain IAPC and the
DBMS specification. So, if you are writing DBMS the message points you
to that webpage, if you are writing plain IPAC it points you to plain
IPAC. I thought uers might be confused to receivea link to IPAC when
they set |DBMS = True| ...