Minor formatting of error message

skimage/io/_plugins/pil_plugin.py

@@ -34,7 +34,7 @@ def imread(fname, dtype=None):
         im.getdata()[0]
     except IOError:
         site = "http://pillow.readthedocs.org/en/latest/installation.html#external-libraries"
-        raise ValueError('Could not load "%s"\nPlease see documentation at  %s' % (fname, site))
+        raise ValueError('Could not load "%s"\nPlease see documentation at: %s' % (fname, site))
     else:
         return pil_to_ndarray(im, dtype)