Cube header not updated in write to file
the header of Cube objects is not updated when written to file
scube=Cube('./subcubeOII_DATACUBE_FINAL_ZAP_J1422_QSO_subtracted.fits')
In [67]: pyfits.open(scube.filename)[1].header['BUNIT']
Out[67]: '10**(-20)*erg/s/cm**2/Angstrom'
In [68]: scube.data_header.set('BUNIT','10**(-20)*erg/s/cm**2')
In [69]: scube.data_header['BUNIT']
Out[69]: '10**(-20)*erg/s/cm**2'
In [70]: rm tmp.fits
rm: remove regular file ‘tmp.fits’? y
In [71]: scube.write('tmp.fits')
In [73]: pyfits.open('tmp.fits')[1].header['BUNIT']
Out[73]: '10**(-20)*erg/s/cm**2/Angstrom'