from datetime import datetime is never given for datetime

I narrowed it down to the [fixup method](https://github.com/alecthomas/importmagic/blob/master/importmagic/index.py#L245) but no real succes in fixing it, except from not calling the method when the symbol is in the path https://github.com/alecthomas/importmagic/compare/master...paradoxxxzero:master but this seems hackish and would not work for module in module in module all with the same name...

Any thoughts?