Merge #14954: build: Require python 3.5

fa2797808e test: Remove python3.4 workaround in feature_dbcrash (MarcoFalke)
dddd1d05d3 .python-version: Specify full version 3.5.6 (MarcoFalke)
faa7cdf764 scripted-diff: Update copyright in ./test (MarcoFalke)
fa0e65b772 scripted-diff: test: Remove brackets after assert (MarcoFalke)
fab5a1e0f4 build: Require python 3.5 (MarcoFalke)
fa6bf21f5e scripted-diff: test: Use py3.5 bytes::hex() method (MarcoFalke)

Pull request description:

  Python 3.4 is EOL after March 2019, so switch to 3.5. See https://devguide.python.org/#status-of-python-branches

  This pull does the following in a bunch of commits:
  * scripted diff to use the `bytes::hex()` method in place of previous wrappers (`b2x`, `bytes_to_hex_str`, `hexlify`, ...)
  * Update the build system (gitian and travis) to remove python2.7 and replace it with python3.5
  * Another scripted-diff to remove brackets after `assert`. This is unrelated to the python3.5 switch, but a stylistic commit, so probably not worth to split up. The motivation behind it is to avoid asserting on data structures (such as tuples of length one), which never fails:
  ```py
  >>> assert(False,)   # with brackets
  >>> assert False,    # without brackets
  SyntaxError: invalid syntax
  >>> assert False     # proper assertion
  AssertionError
  ```
  * And then a final scripted diff to update the copyright headers in the `test` subfolder, since I touched most of the files anyway and it wouldn't make sense to split this commit out into a separate pull.

  For reference (contributed by luke-jr):

  Ubuntu LTS (bionic): 3.6.5
  Debian stable (stretch): 3.5.3
  RHEL 8 (expected before v0.19): 3.6.x
  Gentoo stable: 3.6.5
  Arch: 3.7.1

Tree-SHA512: 643c28cd2d5b9543ce4bf8ad2a8b282bc79b37dc5b25c9c8358e6ce201e2a67a546463e5f3430b16652eb2489d7c3ed4b0772cd2e2bf790fe68a5e3cc8a25029

1 files changed, 3 insertions, 4 deletions

diff --git a/test/functional/test_framework/blocktools.py b/test/functional/test_framework/blocktools.py
index 15f4502994..7ac044d0d0 100644
--- a/test/functional/test_framework/blocktools.py
+++ b/test/functional/test_framework/blocktools.py
@@ -20,7 +20,6 @@ from .messages import (
     CTxOut,
     FromHex,
     ToHex,
-    bytes_to_hex_str,
     hash256,
     hex_str_to_bytes,
     ser_string,
@@ -132,7 +131,7 @@ def create_tx_with_script(prevtx, n, script_sig=b"", *, amount, script_pub_key=C
        Can optionally pass scriptPubKey and scriptSig, default is anyone-can-spend output.
     """
     tx = CTransaction()
-    assert(n < len(prevtx.vout))
+    assert n < len(prevtx.vout)
     tx.vin.append(CTxIn(COutPoint(prevtx.sha256, n), script_sig, 0xffffffff))
     tx.vout.append(CTxOut(amount, script_pub_key))
     tx.calc_sha256()
@@ -190,7 +189,7 @@ def witness_script(use_p2wsh, pubkey):
         witness_program = CScript([OP_1, hex_str_to_bytes(pubkey), OP_1, OP_CHECKMULTISIG])
         scripthash = sha256(witness_program)
         pkscript = CScript([OP_0, scripthash])
-    return bytes_to_hex_str(pkscript)
+    return pkscript.hex()
 
 def create_witness_tx(node, use_p2wsh, utxo, pubkey, encode_p2sh, amount):
     """Return a transaction (in hex) that spends the given utxo to a segwit output.
@@ -215,7 +214,7 @@ def send_to_witness(use_p2wsh, node, utxo, pubkey, encode_p2sh, amount, sign=Tru
     tx_to_witness = create_witness_tx(node, use_p2wsh, utxo, pubkey, encode_p2sh, amount)
     if (sign):
         signed = node.signrawtransactionwithwallet(tx_to_witness)
-        assert("errors" not in signed or len(["errors"]) == 0)
+        assert "errors" not in signed or len(["errors"]) == 0
         return node.sendrawtransaction(signed["hex"])
     else:
         if (insert_redeem_script):