ImportError from package under test results in 0 tests discovered

[sjagoe]

Adding raise ImportError() to the top-level __init__.py of a project yields this behaviour:

$ haas

----------------------------------------------------------------------
Ran 0 tests in 0.000s

OK

[sjagoe]

The root cause here is a "feature" allowing tests to be discovered in Python 3 packages that lack an __init__.py. That feature will be considered for removal in v0.7.0 (see #113).