Remove lena image from test suite.

Results from the morphology module were compared against output from the
corresponding MATLAB functions, as applied to the lena test image.  This image
does not conform to the Debian Free Software Guidelines and had to be removed.
The output is now tested against results generated with the current version of
scikit-image (0.12.0), which is known to be correct due to the comparison
described above.

skimage/data/__init__.py

@@ -61,13 +61,16 @@ def camera():
 def lena():
     """Colour "Lena" image.
 
+    **This image has been removed from scikit-image due to copyright
+    concerns.**
+
     The standard, yet sometimes controversial Lena test image was
     scanned from the November 1972 edition of Playboy magazine.  From
     an image processing perspective, this image is useful because it
     contains smooth, textured, shaded as well as detail areas.
 
     """
-    return load("lena.png")
+    raise RuntimeError("This image has been removed due to copyright concerns.")
 
 
 def astronaut():

skimage/data/tests/test_data.py

@@ -1,12 +1,11 @@
 import numpy as np
 import skimage.data as data
-from numpy.testing import assert_equal, assert_almost_equal
+from numpy.testing import assert_equal, assert_almost_equal, assert_raises
 
 
-def test_lena():
-    """ Test that "Lena" image can be loaded. """
-    lena = data.lena()
-    assert_equal(lena.shape, (512, 512, 3))
+def test_lena_removed():
+    """ Test that "Lena" has been removed """
+    assert_raises(RuntimeError, data.lena)
 
 
 def test_astronaut():