Add tests where appropriate

[RobertRosca]

Python packages with test methods should have tests added to them.

First thing to include is the install time test callbacks:

class ...
    install_time_test_callbacks = ['import_module_test']
    ...

Also, where package has pytest tests set up, you can use the following to overwrite the default PythonPackage test behaviour to execute pytests:

class ...
    def test(self):
        # `setup.py test` should not be used as:
        #   - `python3 -m pytest -v` should be ran instead
        #   - the builtin `test` method runs before `install` is finished
        self.pytest()

    def pytest(self):
        with working_dir('.'):
            prefix = self.spec.prefix
            #  Add bin to path here, as tests also check entrypoints
            env['PATH'] = env['PATH']+":"+prefix+"/bin"
            python('-m', 'pytest', '-v')
    ...

Where the prefix... and env lines are only required when testing packages that implement entrypoints.