It is quite pointless uploading your files to a website that only allows you to download them once. Just upload the log files to the forums, no need for external services.
Anyway, to come back to your issue, OctoPi 0.15 is too old to be supported on newer versions of OctoPrint. I would suggest creating a backup of your current OctoPrint settings & plugins from the built in backup & restore, then re-flash the latest version of OctoPi (0.18), from OctoPrint.org - Download & Setup OctoPrint.
That will additionally migrate your install to Python 3, as we've been trying to get people to do for the last 18 months and will be a hard requirement for OctoPrint 1.8.0, which is currently in the second release candidate.
If anyone else would like to look at the logs, I've reuploaded them here since they were deleted after downloading from the links above: