.error: Implemented iterability of error typecodes
.error: Implemented iterability of error typecodes

Metaclass approach to allowing iteration over an OPANError subclass
  type to provide the valid typecodes was implemented:

    >>> 'xyzfile' in opan.error.XYZError
    True

Obsolete `typecodes` members of all subclasses were excised.

bskinn/opan,bskinn/opan