Test should be skipped if ipykernel not installed

[aaronayres35]

When running the test suite in an environment in which ipykernel was not installed the following test failure occurs:

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ERROR: tests.test_ids (unittest.loader._FailedTest)
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ImportError: Failed to import test module: tests.test_ids
Traceback (most recent call last):
  File "/Users/aayres/.edm/envs/test-envisage/lib/python3.6/unittest/loader.py", line 428, in _find_test_path
    module = self._get_module_from_name(name)
  File "/Users/aayres/.edm/envs/test-envisage/lib/python3.6/unittest/loader.py", line 369, in _get_module_from_name
    __import__(name)
  File "/Users/aayres/Desktop/envisage/envisage/tests/test_ids.py", line 15, in <module>
    from envisage.plugins.ipython_kernel.api import IPythonKernelPlugin
  File "/Users/aayres/Desktop/envisage/envisage/plugins/ipython_kernel/api.py", line 17, in <module>
    from envisage.plugins.ipython_kernel.actions import StartQtConsoleAction
  File "/Users/aayres/Desktop/envisage/envisage/plugins/ipython_kernel/actions.py", line 13, in <module>
    from .internal_ipkernel import InternalIPKernel
  File "/Users/aayres/Desktop/envisage/envisage/plugins/ipython_kernel/internal_ipkernel.py", line 20, in <module>
    import ipykernel.connect
ModuleNotFoundError: No module named 'ipykernel'


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This test should simply be skipped if ipykernel is not installed

[bnavigator]

closed by #423

[mdickinson]

Thanks; closing. (It looks as though I failed to notice that #420 was a duplicate of this issue.)