[AstroPy] Unnecessary warning "cdelt will be ignored since cd is present"

[Maik Riechert]

Hi,

I use astropy 0.3 and get the warning "cdelt will be ignored since cd is 
present" when I call wcs.printwcs() even though the FITS headers don't 
contain cdelt:

SIMPLE  =                    T / Standard FITS file
BITPIX  =                    8 / ASCII or bytes array
NAXIS   =                    0 / Minimal header
EXTEND  =                    T / There may be FITS ext
WCSAXES =                    2 / no comment
CTYPE1  = 'RA---TAN' / TAN (gnomic) projection
CTYPE2  = 'DEC--TAN' / TAN (gnomic) projection
EQUINOX =               2000.0 / Equatorial coordinates definition (yr)
LONPOLE =                180.0 / no comment
LATPOLE =                  0.0 / no comment
CRVAL1  =        282.428453019 / RA  of reference point
CRVAL2  =        36.6483063538 / DEC of reference point
CRPIX1  =        1938.20328776 / X reference pixel
CRPIX2  =        1163.46704102 / Y reference pixel
CUNIT1  = 'deg     ' / X pixel scale units
CUNIT2  = 'deg     ' / Y pixel scale units
CD1_1   =     -0.0164029166118 / Transformation matrix
CD1_2   =     0.00410727100937 / no comment
CD2_1   =    -0.00410727100937 / no comment
CD2_2   =     -0.0164029166118 / no comment
IMAGEW  =                 4256 / Image width,  in pixels.
IMAGEH  =                 2832 / Image height, in pixels.
HISTORY...
DATE    = '2013-11-29T11:55:49' / Date this file was created.
COMMENT...
END

I know printwcs() is declared as an internal function and I don't get 
the message when I don't call printwcs(), but still, I thought I let you 
know, just in case.

Cheers
Maik