SOURCE_LIST in test_validate_content.py requires internet

[hugobuddel]

scopesim_templates/tests/test_utils/test_validate_content.py requires the internet on collection, because

# Add all initialied examples of sources to be tested to this list
SOURCE_LIST = [star(filter_name="Ks", amplitude=10*u.mag),
               star(filter_name="Paranal/HAWKI.J", amplitude=10*u.Jansky),
               spiral_two_component(),
               galaxy(sed="kc96/s0"),
               galaxy3d(sed="kc96/s0", ngrid=10),
               source_from_array(arr=np.ones(shape=(100, 100)),
                                 sed="kc96/s0",
                                 amplitude=15,
                                 pixel_scale=0.2,
                                 filter_curve="g")
               ]

requires internet