Verifying device integrity. Galaxy Tab S2 9.7"
Custom recoveries and ROMs don't enforce SEAndroid, so the error pops out. Ignore it.
Get stock Samsung images from SamMobile. This is also the surefire way to return to factory recovery (along with everything else).
Please get a screenshot (camera capture) of the failed CM installation, so that we can diagnose what's the issue.
Assuming the flashing process failed at its start, it doesn't even wipe anything, so it's stock Samsung system + TWRP, nothing more.