updated xenial and stretch dockerfiles since they bundle old versions of libsodium
refacatoring to make BlockchainInterface and BitcoinCoreNoHistoryInterface python2 compatible
add the -acceptnonstdtxn flag when invoking bitcoind for versions >= 0.19.0
refactor the use of nonlocal to make it compatible with python2
document the get_bitcoind_version method
Use relative paths when setting btcconf default filepath
Whitespace and newlines
Must specify return value in python
os.path.join preferred over str +
Also adding some print statements.
Kristaps Kaupe
Adam Gibson
Tim Akinbo
James Hilliard
mecampbellsoup