Bandit fails when using importlib with named arguments

[Marcin Kielar]

This code:
```
importlib.import(name='some_name')
```

causes Bandit to fail like this:
```
75 [0.. [tester] ERROR Bandit internal error running: blacklist on file [MASKED]/extension_loader.py at line 52: list index out of rangeTraceback (most recent call last):
  File "[MASKED]/venv/lib64/python3.8/site-packages/bandit/core/tester.py", line 52, in run_tests
    result = test(context, test._config)
  File "[MASKED]/venv/lib64/python3.8/site-packages/bandit/core/blacklisting.py", line 50, in blacklist
    name = context.call_args[0]
IndexError: list index out of range
```

This works okay:
```
importlib.import('some_name')
```