Merge #19287: contrib: Fix SyntaxWarning in Python base58 implementation

47b49a05ea contrib: Fix SyntaxWarning in Python base58 implementation (Alex Willmer)

Pull request description:

  In Python integers should be compared for equality (`i == j`), not identity (`i is j`). Recent versions of CPython 3.x emit a SyntaxWarning when they encounter this incorrect usage, e.g.

  ```
  $ python3 base58.py
  base58.py:110: SyntaxWarning: "is" with a literal. Did you mean "=="?
    assert get_bcaddress_version('15VjRaDX9zpbA8LVnbrCAFzrVzN7ixHNsC') is 0
  Tests passed
  ```

ACKs for top commit:
  MarcoFalke:
    ACK 47b49a05ea

Tree-SHA512: 9f8962025dcdfa062c0515c68a1864f5bbeb86bd0510c0ec0e413a5edb6afbfd5f41b4c0255784e53db8eaf39c68b7cfa7cc8a33a2e5214aae463fda374f8719

contrib/testgen/base58.py

@@ -107,7 +107,7 @@ def get_bcaddress_version(strAddress):
 
 if __name__ == '__main__':
     # Test case (from http://gitorious.org/bitcoin/python-base58.git)
-    assert get_bcaddress_version('15VjRaDX9zpbA8LVnbrCAFzrVzN7ixHNsC') is 0
+    assert get_bcaddress_version('15VjRaDX9zpbA8LVnbrCAFzrVzN7ixHNsC') == 0
     _ohai = 'o hai'.encode('ascii')
     _tmp = b58encode(_ohai)
     assert _tmp == 'DYB3oMS'