Delete the ``MODEL_DATA`` and ``CORRECTED_DATA`` columns from a measurement set.

    mspath (str)
      The path to the MS to modify

    Example::

      from pwkit.environments.casa import tasks
      tasks.delcal('dataset.ms')

def delcal(mspath):
    """Delete the ``MODEL_DATA`` and ``CORRECTED_DATA`` columns from a measurement set.

    mspath (str)
      The path to the MS to modify

    Example::

      from pwkit.environments.casa import tasks
      tasks.delcal('dataset.ms')

    """
    wantremove = 'MODEL_DATA CORRECTED_DATA'.split()
    tb = util.tools.table()
    tb.open(b(mspath), nomodify=False)
    cols = frozenset(tb.colnames())
    toremove = [b(c) for c in wantremove if c in cols]
    if len(toremove):
        tb.removecols(toremove)
    tb.close()

    # We want to return a `str` type, which is what we already
    # have in Python 2 but not in 3.
    if six.PY2:
        return toremove
    else:
        return [c.decode('utf8') for c in toremove]