Add support for Python 3.7

[avylove]

Python 3.7 is scheduled for release on June 15th so I've started testing some of my projects for compatibility. I ran into some issues running blessed due to changes in the the re module. I also added 3.6 and 3.7 to tox and travis and included changes needed to ensure all the tests pass. Summary of the changes is below.

Python 3.7 compatibility

• re.sub: Unknown escapes in repl consisting of '' and an ASCII letter now are errors.

  • blessed/sequences.py
  • Workaround by making repl a function
    pattern = re.sub(r'\d+', _numeric_regex, _outp)
    becomes
    pattern = re.sub(r'\d+', lambda x: _numeric_regex, _outp)

• re.escape: Only characters that can have special meaning in a regular expression are escaped.

  • blessed/sequences.py (affects behavior)
  • blessed/tests/test_core.py (changes)
  • Only test that failed was test_termcap_repr()
    • Returned
      r"<Termcap cursor_up:'\x1b\\[A'>"
      instead of
      r"<Termcap cursor_up:'\\\x1b\\[A'>"
    • Assuming new output is valid since primary purpose is to feed regex and all other tests pass
    • Updated test to expect new output (along with existing)

Fixes for Travis

• Not related to Python 3.7
• Ctrl-C test was inconsistent and configured to be skipped on Travis, but the TRAVIS environment variable was not being passed to tox
  • Added TRAVIS variable to tox environment
• There were some issues in the Travis environment due to the default Python
  • Changed global python to 3.6 before install
  • The Travis environment should be updated soon and we won't need this anymore

Fix issues with static analysis

• Not related to Python 3.7
• Forced prospector not to use external config files
  • This prevents it from using any pylintrc and similar files it finds in it's environment
• Disabled two docstring checks:
  • D212: Multi-line docstring summary should start at the first line
  • D401: First line should be in imperative mood
• Code cleanup to resolve other errors and warnings

Temporarily disabled display-maxcanon.py

• Not related to Python 3.7
• On my system and in Travis, this seems to run forever.
  • Unsure if this is due to a change in pexpect or Linux
  • Considered adding limits, but you're the expert in this, so figured you would know better

[jquast]

My sincere thanks, I'll incorporate this very soon. You are a very kind and careful person, thank you for the good quality!

[avylove]

Any progress on this? Fedora is already starting to build packages against 3.7 in prep for the release at the end of the month.

[jquast]

apologies, will push for release immediately, will comment again soon when complete

[jquast]

should be released...

https://pypi.org/project/blessed/

[avylove]

Awesome! Thanks!

[serhiy-storchaka]

Workaround by making repl a function

Other workaround: duplicate backslashes in the replacement string.

pattern = re.sub(r'\d+', _numeric_regex, _outp)

becomes

pattern = re.sub(r'\d+', _numeric_regex.replace('\\', r'\\'), _outp)

And since r'(\d+)' means the same as r'\d+' in re.sub(), you don't need two branches at lines 131-135.