@dkillick To tie the `_MPL_AVAILABLE` even tighter to your `try-except` block,  you could put it in a `try-except-else` block i.e.
```
try:
    import matplotlib
    ...
except ImportError:
    _MPL_AVAILABLE = False
else:
    _MPL_AVAILABLE = True
```

Just a suggestion, your call ...

Also, is it worth issuing a warning to explicitly tell the user that no graphics tests are being performed ?