Openbazaar python launcher

new pull request after 1st round of reviews.
Thanks @Renelvon this has the merged changes from your repo.

(@Renelvon I kept that REVERT commit you put there as I'm not sure I understood what was right or wrong about it, I figured it'd be easier to fix here now)
will move it outside to crypto_util.

regardless of where the issue should be taken care of, the issue will keep coming back (this was the first issue I dealt with when I first tried running OpenBazaar, had I not been a developer I would've given up on it, having a friendly error message tell you what to do is priceless imo)