Fixing broken stuff

CONTRIBUTING.rst

@@ -53,7 +53,7 @@ To set up `img2cmap` for local development:
 
     pip install img2cmap[dev]
 
-5. When you're done making changes run all the checks and docs builder with `tox <https://tox.readthedocs.io/en/latest/install.html>`_ one command::
+5. When you're done making changes run all the checks and docs builder with `tox <https://tox.wiki/en/latest/installation.html>`_ one command::
 
     tox
 

tests/test_img2cmap.py

@@ -67,7 +67,6 @@ def test_cmap_optimal_plot(test_image_input):
     imageconverter = ImageConverter(test_image_input)
     cmaps, _, _ = imageconverter.generate_optimal_cmap(random_state=42)
     for _, cmap_ in cmaps.items():
-
         assert not np.any(np.all(np.isclose(cmap_.colors, 1, atol=1e-9)))
         assert not np.any(np.all(np.isclose(cmap_.colors, 0, atol=1e-9)))
 
@@ -135,6 +134,6 @@ def test_compute_optimal_hexcodes():
 
 
 def test_break_kneed():
-    with pytest.raises(UserWarning):
+    with pytest.raises(ValueError):
         imageconverter = ImageConverter(image_urls[0])
-        imageconverter.generate_optimal_cmap(max_colors=5, random_state=42)
+        imageconverter.generate_optimal_cmap(max_colors=1, random_state=42)