Ticket #2850 - Ipactl exception not handled well
    
    Ticket #2850 - Ipactl exception not handled well
    
    There were various places in ipactl which intialized IpactlError with
    None as the msg. If you called str() on that exception all was well
    because ScriptError.__str__() converted a msg with None to the empty
    string (IpactlError is subclassed from ScriptError). But a few places
    directly access e.msg which will be None if initialized that way. It's
    hard to tell from the stack traces but I'm pretty sure it's those
    places which use e.msg directly which will cause the problems seen in
    the bug report.
    
    I do not believe it is ever correct to initialize an exception message
    to None, I don't even understand what that means. On the other hand
    initializing to the empty string is sensible and for that matter is
    the default for the class.
    
    This patch makes two fixes:
    
    1) The ScriptError initializer will now convert a msg parameter of
    None to the empty string.
    
    2) All places that initialized IpactlError's msg parameter to None
    removed the None initializer allowing the msg parameter to default
    to the empty string.
    
    I don't know how to test the fix for Ticket #2850 because it's not
    clear how it got into that state in the first place, but I do believe
    initialing the msg value to None is clearly wrong and should fix the
    problem.