AttributeError: 'NoneType' object has no attribute 'group'

The following line raises an AttributeError when the cache is being rebuilt. Seems `re.search ` can return `None`. Not sure what the underlying issue is, but the error should at least exit the method a bit more graceful.

https://github.com/lepisma/pipwin/blob/73e0d9817cf0281e1b012bcf7b12808f9761d895/pipwin/pipwin.py#L103
