Allow for no exceptions to be raised and cleanup

Allow for no exceptions to be raised

Add some helpful comments

Remove doctest skips

Remove TODO note

Cleanup and skip failing doctest

skimage/morphology/watershed.py

@@ -119,9 +119,9 @@ def watershed(image, markers, connectivity=None, offset=None, mask=None):
     >>> from skimage.feature import peak_local_max
     >>> local_maxi = peak_local_max(distance, labels=image,
     ...                             footprint=np.ones((3, 3)),
-    ...                             indices=False)  # doctest: +SKIP
-    >>> markers = ndimage.label(local_maxi)[0]  # doctest: +SKIP
-    >>> labels = watershed(-distance, markers, mask=image)  # doctest: +SKIP
+    ...                             indices=False)
+    >>> markers = ndimage.label(local_maxi)[0]
+    >>> labels = watershed(-distance, markers, mask=image)
 
     The algorithm works also for 3-D images, and can be used for example to
     separate overlapping spheres.