Merge #11881: Remove Python2 support

1874058 Make base58 python contrib code work with python3 (Evan Klitzke)
bc6fdf2 Change all python files to use Python3 (John Newbery)

Pull request description:

  Following discussion here: https://github.com/bitcoin/bitcoin/pull/11843#issuecomment-351033742

  It's easier for maintainers if all python tools/scripts support only a single version of Python. There are only a few scripts that aren't explicitly python3 at this point, so this PR changes those remaining scripts to explicitly require python3.

Tree-SHA512: 5d38eef6e0fc7d8515e23a1f4c75e8b4160fd0fe23cba52a1f41689b114e54a9e503e0724829e8b41982ef98f2d113df80d9e238213b74f09ceaed0344a19e24

contrib/devtools/optimize-pngs.py

@@ -46,7 +46,6 @@ for folder in folders:
             file_path = os.path.join(absFolder, file)
             fileMetaMap = {'file' : file, 'osize': os.path.getsize(file_path), 'sha256Old' : file_hash(file_path)}
             fileMetaMap['contentHashPre'] = content_hash(file_path)
-
             try:
                 subprocess.call([pngcrush, "-brute", "-ow", "-rem", "gAMA", "-rem", "cHRM", "-rem", "iCCP", "-rem", "sRGB", "-rem", "alla", "-rem", "text", file_path],
                                 stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)

contrib/macdeploy/macdeployqtplus

@@ -731,7 +731,6 @@ if config.dmg is not None:
                 hdiutil_args.append(str(value))
 
         return run(hdiutil_args, universal_newlines=True)
-
     if verbose >= 2:
         if fancy is None:
             print("+ Creating .dmg disk image +")

contrib/testgen/gen_base58_test_vectors.py

@@ -74,7 +74,6 @@ def gen_invalid_vector(template, corrupt_prefix, randomize_payload_size, corrupt
         prefix = os.urandom(1)
     else:
         prefix = bytearray(template[0])
-
     if randomize_payload_size:
         payload = os.urandom(max(int(random.expovariate(0.5)), 50))
     else:

doc/release-notes.md

@@ -60,6 +60,11 @@ See detailed [set of changes](https://github.com/dashpay/dash/compare/v0.16.1.0.
 
 - [`ccef3b4836`](https://github.com/dashpay/dash/commit/ccef3b48363d8bff4b919d9119355182e3902ef3) qt: Fix wallet encryption dialog (#3816)
 
+Python Support
+--------------
+
+Support for Python 2 has been discontinued for all test files and tools.
+
 Credits
 =======