Raspberry Pi (Raspbian)
Using a Raspberry Pi with Raspbian it could happen no memory is reported and thus docker_memory fails with an error in line 308 when trying to access values. In such case the Docker API does not report it. Making the following changes, fixes the problem:
Open the file /boot/cmdline.txt
Add the following to the end of the existing line cgroup_enable=cpuset cgroup_memory=1 cgroup_enable=memory
Reboot your Raspberry Pi
NOTE: Add the line to the existing line, do not replace it