Merge #14954: build: Require python 3.5

fa27978 test: Remove python3.4 workaround in feature_dbcrash (MarcoFalke)
dddd1d0 .python-version: Specify full version 3.5.6 (MarcoFalke)
faa7cdf scripted-diff: Update copyright in ./test (MarcoFalke)
fa0e65b scripted-diff: test: Remove brackets after assert (MarcoFalke)
fab5a1e build: Require python 3.5 (MarcoFalke)
fa6bf21 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

Author: MarcoFalke

.python-version

@@ -1 +1 @@
-3.4.9
+3.5.6

.travis.yml

@@ -46,7 +46,7 @@ jobs:
       env:
       cache: false
       language: python
-      python: '3.4' # Oldest supported version according to doc/dependencies.md
+      python: '3.5' # Oldest supported version according to doc/dependencies.md
       install:
         - set -o errexit; source .travis/lint_04_install.sh
       before_script:
@@ -158,7 +158,7 @@ jobs:
       name: 'macOS 10.10  [GOAL: deploy] [no functional tests]'
       env: >-
         HOST=x86_64-apple-darwin14
-        PACKAGES="cmake imagemagick libcap-dev librsvg2-bin libz-dev libbz2-dev libtiff-tools python-dev python3-setuptools-git"
+        PACKAGES="cmake imagemagick libcap-dev librsvg2-bin libz-dev libbz2-dev libtiff-tools python3-dev python3-setuptools-git"
         OSX_SDK=10.11
         RUN_UNIT_TESTS=false
         RUN_FUNCTIONAL_TESTS=false

configure.ac

@@ -85,8 +85,8 @@ AC_PATH_TOOL(RANLIB, ranlib)
 AC_PATH_TOOL(STRIP, strip)
 AC_PATH_TOOL(GCOV, gcov)
 AC_PATH_PROG(LCOV, lcov)
-dnl Python 3.4 is specified in .python-version and should be used if available, see doc/dependencies.md
-AC_PATH_PROGS([PYTHON], [python3.4 python3.5 python3.6 python3.7 python3 python])
+dnl Python 3.5 is specified in .python-version and should be used if available, see doc/dependencies.md
+AC_PATH_PROGS([PYTHON], [python3.5 python3.6 python3.7 python3.8 python3 python])
 AC_PATH_PROG(GENHTML, genhtml)
 AC_PATH_PROG([GIT], [git])
 AC_PATH_PROG(CCACHE,ccache)

contrib/devtools/README.md

@@ -167,7 +167,7 @@ still compatible with the minimum supported Linux distribution versions.
 
 Example usage after a gitian build:
 
-    find ../gitian-builder/build -type f -executable | xargs python contrib/devtools/symbol-check.py 
+    find ../gitian-builder/build -type f -executable | xargs python3 contrib/devtools/symbol-check.py
 
 If only supported symbols are used the return value will be 0 and the output will be empty.
 

contrib/devtools/symbol-check.py

@@ -9,7 +9,7 @@
 
 Example usage:
 
-    find ../gitian-builder/build -type f -executable | xargs python contrib/devtools/symbol-check.py
+    find ../gitian-builder/build -type f -executable | xargs python3 contrib/devtools/symbol-check.py
 '''
 import subprocess
 import re

contrib/gitian-descriptors/gitian-linux.yml

@@ -30,7 +30,7 @@ packages:
 - "faketime"
 - "bsdmainutils"
 - "ca-certificates"
-- "python"
+- "python3"
 remotes:
 - "url": "https://github.com/bitcoin/bitcoin.git"
   "dir": "bitcoin"

contrib/gitian-descriptors/gitian-osx.yml

@@ -23,9 +23,9 @@ packages:
 - "libcap-dev"
 - "libz-dev"
 - "libbz2-dev"
-- "python"
-- "python-dev"
-- "python-setuptools"
+- "python3"
+- "python3-dev"
+- "python3-setuptools"
 - "fonts-tuffy"
 remotes:
 - "url": "https://github.com/bitcoin/bitcoin.git"

contrib/gitian-descriptors/gitian-win.yml

@@ -20,7 +20,7 @@ packages:
 - "nsis"
 - "zip"
 - "ca-certificates"
-- "python"
+- "python3"
 - "rename"
 remotes:
 - "url": "https://github.com/bitcoin/bitcoin.git"

contrib/linearize/README.md

@@ -1,6 +1,5 @@
 # Linearize
-Construct a linear, no-fork, best version of the Bitcoin blockchain. The scripts
-run using Python 3 but are compatible with Python 2.
+Construct a linear, no-fork, best version of the Bitcoin blockchain.
 
 ## Step 1: Download hash list
 

contrib/linearize/linearize-data.py

@@ -16,7 +16,7 @@
 import datetime
 import time
 from collections import namedtuple
-from binascii import hexlify, unhexlify
+from binascii import unhexlify
 
 settings = {}
 
@@ -61,7 +61,7 @@ def calc_hash_str(blk_hdr):
     hash = calc_hdr_hash(blk_hdr)
     hash = bufreverse(hash)
     hash = wordreverse(hash)
-    hash_str = hexlify(hash).decode('utf-8')
+    hash_str = hash.hex()
     return hash_str
 
 def get_blk_dt(blk_hdr):
@@ -213,7 +213,7 @@ def run(self):
 
             inMagic = inhdr[:4]
             if (inMagic != self.settings['netmagic']):
-                print("Invalid magic: " + hexlify(inMagic).decode('utf-8'))
+                print("Invalid magic: " + inMagic.hex())
                 return
             inLenLE = inhdr[4:]
             su = struct.unpack("<I", inLenLE)