Merge #14884: Travis: enforce Python 3.4 support through linter

31926ee [test] functional framework: add CScript hex() for Python 3.4 (Sjors Provoost)
74ce326 [test] Travis: enforce Python 3.4 support in functional tests (Sjors Provoost)

Pull request description:

  The minimum supported version of Python is 3.4 according to [dependencies.md](https://github.com/bitcoin/bitcoin/blob/master/doc/dependencies.md). This PR makes the Travis linter use this version in order to catch accidental use of modern syntax.

Tree-SHA512: 71b2c102be72b135a8ba049378d66875760f20a04a657102a399240c5c2b2ddbdfa7d5ab4c0c0242ecc3259e0ee8eb2273f331bc5eb824f4ae4c3cc58aea37ac

.python-version

@@ -0,0 +1 @@
+3.4.9

.travis.yml

@@ -43,7 +43,7 @@ jobs:
  env:
  cache: false
  language: python
- python: '3.6'
+ python: '3.4' # Oldest supported version according to doc/dependencies.md
  install:
  - set -o errexit; source .travis/lint_04_install.sh
  before_script:

test/functional/test_framework/script.py

@@ -450,6 +450,10 @@ def join(self, iterable):
  # join makes no sense for a CScript()
  raise NotImplementedError
 
+ # Python 3.4 compatibility
+ def hex(self):
+ return hexlify(self).decode('ascii')
+
  def __new__(cls, value=b''):
  if isinstance(value, bytes) or isinstance(value, bytearray):
  return super(CScript, cls).__new__(cls, value)

test/lint/check-doc.py

@@ -26,8 +26,12 @@
 
 
 def main():
- used = check_output(CMD_GREP_ARGS, shell=True, universal_newlines=True, encoding='utf8')
- docd = check_output(CMD_GREP_DOCS, shell=True, universal_newlines=True, encoding='utf8')
+ if sys.version_info >= (3, 6):
+ used = check_output(CMD_GREP_ARGS, shell=True, universal_newlines=True, encoding='utf8')
+ docd = check_output(CMD_GREP_DOCS, shell=True, universal_newlines=True, encoding='utf8')
+ else:
+ used = check_output(CMD_GREP_ARGS, shell=True, universal_newlines=True) # encoding='utf8'
+ docd = check_output(CMD_GREP_DOCS, shell=True, universal_newlines=True) # encoding='utf8'
 
  args_used = set(re.findall(re.compile(REGEX_ARG), used))
  args_docd = set(re.findall(re.compile(REGEX_DOC), docd)).union(SET_DOC_OPTIONAL)