python: catch missing import

Author: scivision

+stdlib/+python/private/pythonException.m

@@ -1,8 +1,8 @@
 function pythonException(e)
 
 switch e.identifier
-  case 'MATLAB:Python:PythonUnavailable'
-    % pass
+  case {'MATLAB:Python:PythonUnavailable', 'MATLAB:undefinedVarOrClass'}
+    % Python not available or Python imported module not available
   case 'MATLAB:Python:PyException'
     if ~contains(e.message, ["is not in the subpath of", "NotADirectoryError", "FileNotFoundError"])
       rethrow(e)

test/TestBackend.m

@@ -6,7 +6,7 @@
 % *   Alternative: install a temporary Python environment, set pyenv to that, then delete that Python install
 
 classdef (SharedTestFixtures={ matlab.unittest.fixtures.PathFixture(fileparts(fileparts(mfilename('fullpath'))))}, ...
-          TestTags = {'impure'}) ...
+          TestTags = {'R2019b', 'impure'}) ...
     TestBackend < matlab.unittest.TestCase
 
 properties