Downloads the Peek & Graves (2010) dust map, placing it in
    the data directory for :obj:`dustmap`.

def fetch():
    """
    Downloads the Peek & Graves (2010) dust map, placing it in
    the data directory for :obj:`dustmap`.
    """
    doi = '10.7910/DVN/VBSI4A'
    
    for component in ['dust', 'err']:
        requirements = {'filename': 'PG_{}_4096_ngp.fits'.format(component)}
        local_fname = os.path.join(
            data_dir(),
            'pg2010', 'PG_{}_4096_ngp.fits'.format(component))
        print('Downloading P&G (2010) {} data file to {}'.format(
            component, local_fname))
        fetch_utils.dataverse_download_doi(
            doi,
            local_fname,
            file_requirements=requirements)