STYLE: src/Python: Fix "do not compare types, use 'isinstance()'" issue

See https://www.python.org/dev/peps/pep-0290/#id23


Former-commit-id: ce86ea30

.flake8

 [flake8]
 max-line-length = 150
 ignore =
-    # E721 do not compare types, use 'isinstance()'
-    E721,
     # F403 'from numpy import *' used; unable to detect undefined names
     F403,
     # F403 'from vtk import *' used; unable to detect undefined names

src/Python/Utilities/LUTUtilities.py

@@ -154,7 +154,7 @@ class LUTUtilities(object):
         '''
         if len(rgba1) != len(rgba2):
             return False
-        if type(rgba1) == type(''):
+        if isinstance(rgba1, str):
             return rgba1 == rgba2
         if len(rgba1) == 3 or len(rgba1) == 4:
             for i in range(0, len(rgba1)):