Enable tethering on Nexus 6 Marshmallow stock and w/o root

enable_tether.sh

# Download latest TWRP from https://dl.twrp.me/shamu
#curl -L -J -O https://dl.twrp.me/shamu/twrp-2.8.7.1-shamu.img
curl -L -J -O https://dl.twrp.me/shamu/twrp-3.0.0-1-shamu.img

# Install the Android SDK tools (need fastboot and adb)
# Boot to bootloader using key combo or adb
adb reboot bootloader

# Ensure bootloader is unlocked in 'Developer Options'
# If you flashed Marshmallow, this should already be set
fastboot oem unlock

# Boot TWRP image w/o flashing it
#fastboot boot twrp-2.8.7.1-shamu.img
fastboot boot twrp-3.0.0-1-shamu.img

# Mount the system partition using TWRP
# Click 'Mount', then check the 'System' box

# Pull the build.prop
adb pull /system/build.prop

# Add the tethering line - this will add "net.tethering.noprovisioning=true" just after "net.bt.name" line.
perl -pi -e '$_ .= qq(net.tethering.noprovisioning=true\n) if /net\.bt\.name/' build.prop

# Push the file back and ensure correct permissions
adb push build.prop /system
adb shell chmod 644 /system/build.prop

# Done.
echo "Done. Reboot phone. After confirming success, you should re-lock bootloader."

Verizon user here, Nexus 6 purchased through Google on Android n beta. The above does not work for me. I even replied the file to verify the line and also advise shell into the system to verify child 644.