Use itertools.combinations when sweeping

[adlai]

>>> create_combination(['apple', 'orange', 'pear', 'orange'], 3)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "lib/common.py", line 358, in create_combination
    assert len(result) == nCk(len(li), n)
AssertionError

[chris-belcher]

Thanks for the PR

Did this cause a crash in a real life usage?

That function is due to be deleted anyway #48

>>> import itertools
>>> [i for i in itertools.combinations(['apple', 'orange', 'pear', 'orange'], 3)]
[('apple', 'orange', 'pear'), ('apple', 'orange', 'orange'), ('apple', 'pear', 'orange'), ('orange', 'pear', 'orange'

[chris-belcher]

This doesn't actually work out the mathematical correct number for a list with repeated elements. If you're going to use less-than instead of equals you might as well remove the assert totally.