On Ubuntu 18.04

1. Does not run as is on vanilla ubuntu 18.04. The default path for python is /usr/bin/python3
2. Manually install python2.7 then the shebang needs to be altered to run:
   #!/usr/bin/python2.7
3. If shebang is altered to /usr/bin/python3 the following error is produced:
   sudo ./pvshrink /dev/sdf
   Traceback (most recent call last):
   File "./pvshrink", line 55, in
   for seg in pvs.split("\n"):
   TypeError: a bytes-like object is required, not 'str'