purple: Fix crash on file transfer requests from unknown contacts. This was the result of an incomplete fix in the previous release and may result in remote DoS. Read the full security advisory at: https://bugs.bitlbee.org/ticket/1282
After some investigation we decided to reclassify a crash fix from the previous release as a security issue. Read the full security advisory at: https://bugs.bitlbee.org/ticket/1281
Included help.txt in the release tarball, which was missing in the previous release and resulted in adding python as a build dependency. The release tarball of 3.5.1 does not require python.