Python3 on Ubuntu LTS20.04

[btcschellingpt]

Ubuntu LTS20.04 uses Python 3.8 as the default version which means the default script fails when invoking "python". This is easily rectified by altering the the "python" invocations (lines 30 and 34) to "python3".

Not sure if this is best resolved with an addendum to README or attempting to identify the active python version and then invoke appropriately.. because RTFM always works so well right?

[nolim1t]

this (#6) might fix it