class_docstr: Test the Scene object's `.load` method for composites.
class_docstr_tok: ["Test","the","Scene","object","'s","`",".load","`","method","for","composites","."]
docstr: Test loading a composite that has a non-existent prereq.
code: def test_load_comp8(self):
      """Test loading a composite that has a non-existent prereq."""
      scene = Scene(filenames=["fake1_1.txt"], reader="fake1")
      pytest.raises(KeyError, scene.load, ["comp8"])
  
imports: from unittest import mock
  import pytest
  import xarray
  from dask import array
  from satpy import Scene
  from satpy.tests.utils import make_cid, make_dataid, make_dsq, spy_decorator
label_desc: Use image node_id 4 for calling the TestLoadingComposites obj's underlying member method code with example usage: obj.test_load_comp8() without return types